Adiponitrile production by the electrolytic hydrodimerization of acrylonitrile

ABSTRACT

THE ELECTROLYTIC HYDRODIMERIXZATION OF ACRYLONITRILE USING AN EMULSION HAVING AN OIL PHASE AND A CONTINUOUS AQUEOUS PHASE, THE ACRYLONITRILE BEING DISTRIBUTED IN THE AQUEOUS PHASE AS DISSOLVED ACRYLONITRILE AND IN THE OIL PHASE IN SUFFICIENT QUANTITY TO SUPPLY ADDITIONAL ACRYLONITRILE TO THE AQUEOUS PHASE UPON ACRYLONITRILE DEPLETION IN THAT PHASE. THE CONCENTRATION OF THE DISSOLVED ACRYLONITRILE IN THE AQUEOUS PHASE IS PREFERABLY MAINTAINED BELOW ABOUT 5% BY WEIGHT AND A QUATERNARY AMMONIUM COMPOUND IS PREFERABLY UTILIZED AS THE SUPPORTING ELECTROLYTE SALT. THE EMULSION PREFERABLY CONTAINS AN ANION POLYMERIZATION INHIBITOR TO SUPPRESS ELECTRIC CURRENT-INDUCED ACRYLONITRILE POLYMERIZATION AND PREFERABLY A PROTECTIVE COLLID IS PRESENT. THE USE OF THIS ANION POLYMERIZATION INHIBITOR AND PREFERABLY THE USE OF THE PROTECTIVE COLLOID IS ALSO APPLICABLE WHEN OPERATING IN THE CONVENTIONAL MANNER UTILIZING A CONVENTIONAL SOLUTION AS OPPOSED TO AN EMULSION FOR THE ELECTROLYSIS.

United States Pate 3 595 764i ADIPONITRILE PnonnciioN av ELECTRO- gYTlC HYDRUDIMERIIZATHON F ACRYLONI- RILE Maomi Seko and Kazuhilro Mihara, Tokyo, Shinsaku Ogawa and Shoichiro Kumazalri, Yokohama, and lRyozo Komori and Muneo Yoshida, Kawasaki, .lapan, assignors to Asahi Kasei Kogyo Kabushilri Kaisha, Osaka, Japan No Drawing. Filed May 31, 1967, Ser. No. 642,321 Claims priority, application Japan, June 14-, 1966, 41/257,988, ll/37,989, ll/37,990

lint. Cl. (307i) 1/00 US. Cl. 204-73 52 Claims ABSTRACT @lF THE DISCLOSURE The electrolytic hydrodimerization of acrylonitrile using an emulsion having an oil phase and a continuous aqueous phase, the acrylonitrile being distributed in the aqueous phase as dissolved acrylonitrile and in the oil phase in sufficient quantity to supply additional acrylonitrile to the aqueous phase upon acrylonitrile depletion in that phase. The concentration of the dissolved acrylonitrile in the aqueous phase is preferably maintained below about 5% by weight and a quaternary ammonium compound is preferably utilized as the supporting electrolyte salt. The emulsion preferably contains an anion polymerization inhibitor to suppress electric current-induced acrylonitrile polymerization and preferably a protective colloid is present. The use of this anion polymerization inhibitor and preferably the use of the protective colloid is also applicable when operating in the conventional manner utilizing a conventional solution as opposed to an emulsion for the electrolysis.

This invention relates to the production of adiponitrile by the electrolytic hydrodimerization of acrylonitrile.

It is known that if a solution of acrylonitrile containing a supporting electrolyte salt is electrolyzed, the same may be converted to adiponitrile at the cathode. Attempts to utilize this electrolytic hydrodimerization in a practical manner have presented difficulties. In general the yield of adiponitrile is relatively low and the electrolysis has low efiiciency. The natural solubility of acrylonitrile in an aqueous solution is relatively low when an electrolyzing a solution containing these relatively low amounts of acrylonitrile it has been found that very little adiponitrile and predominantly propionitrile is formed.

One prior art proposal seeks to overcome this disadvantage by utilizing a supporting electrolyte salt which will allow the dissolution of substantially larger quantities of the acrylonitrile in the solution which is subjected to the electrolysis. In order to obtain any true beneficial eifect in suppressing propionitrile formation, however, relatively large quantities of acrylonitrile greatly in excess of must be maintained dissolved in solution. As lower concentrations approaching 10% are used the process becomes uneconomical due to increasing propionitrile formation, and as the concentration approaches 5% practically no adiponitrile is formed. Supporting electrolyte salts which will solubilize the acrylonitrile in the aqueous solution used for the electrolysis are relatively expensive and furthermore, as the concentration of the dissolved acrylonitrile increases so does the tendency to form trimers and high molecular Weight polymerization products. While it has been proposed to add free radical polymerization inhibitors to the solution being electrolyzed in order to prevent this, this has proven ineffective.

It has also been proposed to effect the electrolysis utilizing sodium hydroxide as the supporting electrolyte and an auxiliary agent containing hydrophilic and hydrophobic groups in order to increase the solubility of the acrylonitrile and to maintain an excess of acrylonitrile in order to assure its disssolution to the maximum extent possible. With the use of the sodium hydroxide, or a sodium hydroxide precursor supporting electrolyte salt however, the pH of the solution increases to a relatively high value generally around 12 and above, and under these conditions it has been found that undesirable biscyanoethylether formation occurs unless the temperature is maintained below 5 C. Furthermore, the presence of excess undissolved acrylonitrile in the area of the electrolysis causes polymerization which not only causes a decreasing yield, but which may interfere with the continued operation of the cell.

None of the prior art proposals have proven completely satisfactory or practical for the commercial electrolytic hydrodimerization of acrylonitrile to adiponitrile.

One object of this invention is a novel process for the electrolytic hydrodimerization of acrylonitrile which avoids the prior art difiiculties and problems.

A further object of this invention is a novel process for the electrolytic hydrodimerization of acrylonitrile which will allow the use of relatively small quantities of dissolved acrylonitrile while at the same time suppressing propionitrile formation and allowing adiponitrile production in yields and efficiency heretofore unattainable.

A still further object of this invention is the elimination of the prior art problem of trimer and higher polymer formation in the electrolytic production of adiponitrile from acrylonitrile.

These and still further objects will become apparent from the following description.

DEFINITIONS nitrile such as Z-cyanoethyl adiponitrile, or the like.

Polymer--A low molecular Weight polymer of acrylonitrile having a molecular weight of more than about 500 as determined by intrinsic viscosity.

Anion polymerization inhibitor-An additive which will inhibit or suppress polymerization initiated by an electric current or field or potential as opposed to free radical induced polymerization, i.e. an inhibitor which will suppress polymerization which proceeds through an anion mechanism, as opposed to the free radical mechanism. A free radical polymerization inhibitor which solely operates by inhibiting free radical formation, i.e. a free radical polymerization inhibitor is to be distinguished from the anion polymerization inhibitor as defined herein.

In accordance with the invention adiponitrile is produced by passing an electrolyzing electric current through an emulsion having an oil phase and a continuous aqueous phase, the emulsion containing a supporting electrolyte salt, acrylonitrile and preferably an anion polymerization inhibitor. The acrylonitrile must be distributed in the aqueous phase as dissolved acrylonitrile and in the oil phase in sufiicient quantity to supply additional acrylonitrile to the aqueous phase upon acrylonitrile depletion in that phase. The electrolysis is effected utilizing any of the known or conventional electrolysis cells and it is important to note that the liquid in the area of the cathode where the desired electrolytic action occurs must be truly in the form of the emulsion and the emulsified oil phase must be in the area of the surface of the cathode. Thus, in accordance with the invention, a true electrolysis of an emulsion occurs which should be distinguished from the case where the electrolysis is eifected utilizing a solution which may contain excess acrylonitrile, or even emulsified acrylonitrile particles away from the area of the cathode surface to facilitate dissolution and maintain acrylonitrile saturation of the solution.

When reference is made herein and in the claims to passing an electrolyzing electric current through an emulsion, this is specifically limited to this case where the emulsion itself is in contact with the cathode where the electrolytic conversion occurs.

Since a suflicient quantity of the acrylonitrile must be distributed in the oil phase to allow transfer of additional acrylonitrile in the solution in the aqueous phase, upon depletion of the dissolved acrylonitrile in that phase, the amount of acrylonitrile dissolved in the aqueous phase and present in the oil phase will tend toward equilibrium conditions. In many instances under these equilibrium conditions, particularly when the acrylonitrile constitutes the bulk of the oil phase, the aqueous phase will tend to maintain itself saturated with acrylonitrile. The anion polymerization inhibitor should preferably be present in amounts sufiicient to suppress electric current induced polymerization of acrylonitrile and should most preferably be present in both the aqueous and oil phases.

The electrolysis, as mentained, may be effected in any of the known or conventional cells. Most preferably the electrolysis is effected in a cell provided with a diaphragm separating the cathode compartment from the anode compartment and provided with means for separately circulating the anolyte and catholyte. As the supporting electrolyte salt utilized in the cell or in the catholyte where a diaphragm-type cell is used, any salt which will render the catholyte conductive, which will not discharge at the cathode, and which will allow the acrylonitrile to be hydrodimerized by the electrolysis may be used.

There may be mentioned as these salts organic or inorganic salts of the alkali or alkaline earth metals, as for example salts of lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium and barium. Ammonium salts and quaternary ammonium salts of organic and inorganic acids may also be used. Preferred are quaternary ammonium salts, such as sulfates, halides, sulfonates, alkylsulfonates, or salts of organic acid such as acetates, etc. and their derivatives. Especially preferred are aliphatic quaternary ammonium salts, aromatic quaternary ammonium salts, heterocyclic quaternary ammonium salts, i.e. tetraalkyl ammonium salts, tetraalkanol ammonium salts, alkyltrialkanol ammonium salts, dialkyldialkanol ammonium salts, alkanoltrialkanol ammonium salts, N-heterocyclic N-alkyl ammonium salts. As anions of supporting electrolyte salt, anions of organic and inorganic acids can be used. Preferable are sulfate, chloride, bromide, iodide, perchlorate, phosphate and chlorosulfonate anions, anions of sulfonic acid namely aryl sulfonic acid and alkaryl sulfonic acid, for example, benzene sulfonic acid, m-, or p-toluene sulfonic acid, 0-, mor p-ethylbenzene sulfonic acid, o, mor p-cumene sulfonic acid, o-, mor p-tertiary amylbenzene sulfonic acid, o-, mor p-hexylbenzene sulfonic acid, oor p-xylene-4-sulfonic acid, m-xylene-4- or 5-sulfonic acid, mesitylene-Z- sulfonic acid, durene-3-sulfonic acid, pentamethylbenzene sulfonic acid, o-dipropylbenzene-4-sul-fonic acid, alphaor beta-naphthalene sulfonic acid, o-, mor p-biphenyl sulfonic acid and alpha-methyl-beta-naphthalene sulfonic acid, methane sulfonic acid, ethane sulfonic acid, lauryl sulfonic acid anions, and anions of alkylsulfuric acid, for example, methyl sulfuric acid, ethyl sulfuric acid anions and the anions of carboxylic acids, for example, formic acid, acetic acid, propionic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, hexahydrobenzoic acid, nicotinic acid, oxalic acid, malonic acid, adipic acid, fumaric acid, maleic acid, tartaric acid, phthalic acid and phenylacetic acid anions, etc. Among these anions, those which can be easily reduced at the cathode might cause disadvantages for hydrodimerizing acrylonitrile. Generally the supporting electrolyte salt can be prepared of any kind of the aforesaid cations and anions. Most preferred are quaternary ammonium sulfate compounds, as for example, tetramethyl ammonium sulfate, tetraethyl ammonium sulfate, tetrapropyl ammonium sulfate, tetrabutyl ammonium sulfate, trimethylethanol ammonium sulfate, methylpyridinium sulfate, ethylpyridinium sulfate, trimethylbenzyl ammonium sulfate, triethylbenzyl ammonium sulfate, phenyltrimethyl ammonium sulfate, phenyltriethyl ammonium ethyl sulfate, tetramethyltoluidene diammonium sulfate, and quaternary ammonium sulfates, such as tetraethyl ammonium toluene sulfonate, tetraethyl ammonium benzene sulfonate, tetraethyl ammonium cumene sulfonate, tetraethyl ammonium-p-ethylbenzene sulfonate, tetramethyl ammonium benzene sulfonate, tetramethyl ammonium toluene sulfonate, N,N-dimethyl piperidinium-o-toluene sulfonate, N,N'-dimethyl piperidinium toluene sulfonate, N,N'-dimethyl piperidinium bisphenyl sulfonate, tetrabutyl ammonium naphthalene sulfonate, tetra butyl ammonium toluene sulfonate, tetrapropyl ammonium amylbenzene sulfonate, tetrapropyl ammonium-alphaethyl-beta-naphthalene sulfonate, tetraethanol ammoniump-toluene sulfonate, tetraethanol ammonium cumene sulfonate, tetrabutanol ammonium benzene sulfonate, tetrabutanol ammonium xylene sulfonate, tetrapentyl ammonium-o-toluene sulfonate, tetrapentyl ammonium hexylbenzene sulfonate, tetrapentanol ammonium-p-cumene-3- sulfonate, tetrapentanol ammonium benzene sulfonate, methyltriethyl ammonium toluene sulfonate, methyltriethyl ammonium mesitylene-Z-sulfonate, trimethylethyl ammonium sulfonate, trimethylethyl ammonium toluene sulfonate, triethylpentyl ammonium-alpha or beta-naphthalene sulfonate, trimethylpentyl ammonium butylbenzene sulfonate, trimethylethanol ammonium benzene sulfonate, trimethylethanol ammonium toluene sulfonate, N,N'-diethylpiperidinium hexylbenzene sulfonate, N-methylpyrrodinium hexylbenzene sulfonate, N,N'-di-ethylpiperidinium toluene sulfonate, N-methylpyrrodinium toluene sulfonate, N,N-diisopropyl morpholinium toluene sulfonate, N,N'-dibutyl morpholinium sulfonate, N,N-diisopropylbiphenyl morpholinium sulfonate, N,N'-dibutyl morpholinium-p-biphenyl sulfonate, phenyltriethyl ammonium toluene sulfonate, trimethylphenyl ammonium benzene sulfonate, trimethylnaphthyl ammonium toluene sulfonate, dimethylbenzylphenyl ammonium toluene sulfonate, dibenzylethylphenyl ammonium toluene sulfonate, or the like, and alkyl sulfonates, halides, phosphates, and alkali metal sulfonates such as tetramethyl ammonium methyl sulfate, tetraethyl ammonium ethyl sulfate, trimethylethyl ammonium ethyl sulfate, trimethylethylmethylphenyl ammonium sulfate, phenyltrimethyl ammonium halide, tetraethyl ammonium halide, tetrapropyl ammonium halide, tetrabutyl ammonium halide, potassium toluene sulfonate, sodium benzene sulfonate, potassium toluene sulfonate and benzyltrimethyl ammonium phosphate, etc.

While in certain literature primary, secondary and tertiary amine compounds have been mentioned as supporting electrolyte salts, the same are not suitable in accordance with the invention as we have found when using these salts predominantly propionitrile is produced. These primary, secondary and tertiary amine salts should therefore not be considered as suitable supporting electrolyte salts in accordance with the invention.

The particular supporting electrolyte salt to be chosen will depend on the desired conditions of operation and the desired concentration of dissolved acrylonitrile to be maintained in the aqueous phase of the emulsion. If it is desired to maintain higher concentrations of dissolved acrylonitrile, it is necessary to use a supporting electrolyte salt containing hydrophobic, i.e. oleophilic groups, as for example, alkyl, aryl or alkylaryl quaternary ammonium sulfonic salts, or to additionally utilize a solubilizer for the acrylonitrile, such as an alkyl, aryl or alkaryl sulfonate or sulfate.

If, on the other hand in accordance with the preferred embodiment of the invention it is desired to maintain a low concentration of dissolved acrylonitrile in the aqueous phase, and most preferably concentration below about it is preferred to use as the supporting electrolyte salt, salts having low oleophilic properties, i.e. of limited capability of dissolving the acrylonitrile in the aqueous phase, as for example, quarternary ammonium sulfates or halides, which have an added advantage from the standpoint of economy.

The amounts of the supporting electrolyte salt may vary over wide limits depending on the desired operating con ditions, and may for example, vary between 1 and 60% by weight, though generally quantities between about by weight are preferred, the amounts referring to the entire catholyte liquid. The quantity and type of the supporting electrolyte salt should be so chosen that the pH of the catholyte may be maintained between about 1 and 10, and preferably 3 to 9. The supporting electrolyte salt may be distributed according to equilibrium considerations between the aqueous and oil phases of the emulsion, but its presence is only actually required in the aqueous phase.

The emulsion containing the acrylonitrile may be formed in any known or conventional manner by emulsifying the acrylonitrile or a mixture of the acrylonitrile with another organic material as hereinafter described. The emulsification may be effected by mixing, stirring or shaking the materials together, or by using any of the known mechanical emulsifying devices or mixers. Conventional emulsifiers, such as surface active agents, and/or protective colloids, may be added. As preferred examples of protective colloids there may be mentioned protein materials, carboxylic methyl cellulose, methyl cellulose, ethyl cellulose, and traganth. Preferred examples of surface active agents include any of the known soaps or synthetic detergents, as

for example alkyl benzol sulfonates. Conventional amounts of the protective colloids and surface active agents for the purpose intended may be used, which amounts vary between 10 p.p.rn. and 10% by weight. The amount of the oil phase in relation to the aqueous phase may vary within wide limits from 5 times by weight to of the weight, most preferably between 3 times and times the weight of the aqueous phase. The amount of dissolved acrylonitrile in the aqueous phase may also vary within wide limits and may range from as low as by weight to as high as by weight. The natural water solubility of acrylonitrile within the operating temperature range to be encountered does not exceed 10% and is generally in the range of about 7%, so that if larger concentrations are to be maintained in the aqueous phase, it is necessary to use an electrolyte supporting salt, or an auxiliary agent having surface-active characteristics, i.e. hydrophilic and hydrophobic groups, as is known in the art. It is preferable, however, in accordance with the invention to maintain a relatively low concentration of dissolved acrylonitrile as when operating in accordance with this teaching of the invention it becomes possible and feasible for the first time to obtain a high conversion of the acrylonitrile to adiponitrile Without pr'opionitrile formation, and the use of the lower concentration of the dissolved acrylonitrile offers the advantage of minimized oligomer formation and oifers more economical operating conditions. It is thus preferable in accordance wtih the invention to maintain the concentration of dissolved acrylonitrile at a value of less than 5%, and most preferably between 2 and 5% by weight.

In order to maintain this preferable low concentration of dissolved acrylonitrile in the aqueous phase of the emulsion, it may become necessary to dissolve an organic diluent in the aqueous phase. This diluent may constitute any non-reactive aliphatic or aromatic compound which is partially, and preferably only slightly soluble in the aqueous phase of the emulsion so as to partially replace and thus reduce the quantity of acrylonitrile dissolved in the aqueous phase. It has been found most preferable to utilize materials of the type formed in the electrolysis such as adiponitrile and/or propionitrile as the diluent in an amount sufficient to adjust concentration of the dissolved acrylonitrile in the aqueous phase.

Examples of other diluents which may be used include polar or non-polar solvents, such as acetonitrile, dioxane, dimethyl formaldehyde, dimethyl acetoamide, benzol, benzenes, pentane, heptane, hexane, petroleum ether and the like. In some cases it has been preferable to utilize the electrolysis product after processing or purification as the diluent.

The content of the organic diluent may vary between 1 and 50% by weight and naturally a portion thereof distributes itself in the oil phase of the emulsion. Such diluent or diluents may constitute any desired portion of the oil phase and may constitute from about 1 to 99% by weight of this phase. The concentration of the acrylonitrile in the oil phase need only be sufiicient so that the acrylonitrile is available to pass into solution in the aqueous phase upon a lowering of the acrylonitrile concentration in that aqueous phase. For this purpose the concentration of the acrylonitrile in the oil phase should be more than 1%, and should be preferably at least 20%, and most preferably between about 20 and by weight. The supporting electrolyte salt may also distribute in the oil phase, depending on its solubility, and the amount of the supporting electrolyte salt in this phase may, for example, vary between about 0 and 50% by Weight.

As the anion polymerization inhibitor any of the known inhibitors for polymerization which proceeds through an anion mechanism may be used. Thus any of the compounds which are generally effective for the prevention of anion polymerization may be used in accordance with the invention for prevention of polymerization during the electrolysis. In general the anion polymerization inhibitors are compounds which will reduce the negativity of a double bond and which will also prevent acrylonitrile from covering the surface of the cathode by stabilizing the emulsion in the neighborhood of the cathode and thus assuring that the cathode will be contacted by the emulsion. It is preferable that the anion polymerization inhibitor be present in both the oil and aqueous phase of the emulsion and accordingly anion polymerization inhibitors having polar and nonpolar, i.e. oleophilic and hydrophilic groups are preferred. Particularly useful are compounds having active hydrogen, such as amines, ammonia, salts of amines and ammonia, alcohols, organic and inorganic acetates, acetylene compounds and the like. Water is a compound having active hydrogen, but will not function by itself as an anion polymerization inhibitor in accordance with the invention. It has, however, been found that water in combination with a protective colloid, such as one of the protective colloids mentioned previously, will effectively act as an anion polymerization inhibitor and this combination is included as an anion polymerization inhibitor in accordance with the invention. Oxygen and oxygen-containing compounds, such as carbon monoxide, carbon dioxide and carboxyl sulfate may also be used, as may sulfur compounds, such as mercaptans, carbonyl sulfide, carbon disulfide and dialkyl sulfides.

Example of suitable anion polymerization inhibitors include inorganic acids, carboxylic acid compound and sulfonic acid compound especially having alkaryl-, aryland aralkyl sulfouic radicals as these compounds have both hydrophilic and oleophilic radicals. The amine compound may be ammonia, primary, secondary, tertiary amines or their salts having as anions organic or inorganic acid radicals, carbonate, aryl-, alkarylor aralkyl sulfonic acid radicals or alkyl sulfate radicals. Eifective amines may be primary, secondary or tertiary amines or aliphatic or aromatic heterocyclic amines, e.g. monoalkyl amines,

monoalkanol amines, dialkanol amines, piperidine, pyrrolidine or morpholine, alkylene diamines and polyalkylene polyamines, etc. Especially preferred as anion polymerization inhibitors are ammonia, ammonium chloride, ammonium salts of mineral acid such as sulfuric acid, ammonium paratoluene sulfonate, ammonium benzene sulfonate, ammonium methane sulfonate, ammonium laurylsulfonate, amines or amine salts such as methylamine ethylamine, propylamine, butylamine, amylamine, aminopentene, hexylamine, allylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, di-sec-butylamine, di-n-amylamine, methyl-ethylamine, trimethylamine, triethylamine, 2,2',2"-trichlorotriethylamine, trin-propylamine, tri-n-butylamine, triisobutylamine, tri-namylamine, methyldimethylamine, ethylenediamine, propylenediamine, trimethylenediamine, 1,3-diaminobutane, 1,4-diaminobutane, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, spermine, cyclohexylamine, dicyclohexylamine, aniline, 2-aminobiphenyl-, 4- aminobiphenyl-, alpha naphthylamine, beta-naphthylamine, mand p-toluidine, o-3-xylidine, o-4-xylidine, m-2-xylidine, m-4-xylidine, m-5-xylidine, p-Z-cumidine, pcumidine, pseudocumidine, mesidine, o-, mand p-chloroaniline, 2,5-dichloroaniline, o-, mand p-nitroaniline, oand panisidine, cresidine, oand p-phenetidine, 5-nitro-2- bromoxyaniline, benzylamine, beta-phenylethylamine, diphenylamine, phenyl-alpha-naphthylamine, phenyl-betanaphthylamine, monomethylaniline, triphenylamine, dimethylaniline, diethylaniline, ethylbenzylaniline, o-, mand p-phenylenediamine, mand p-toluilenediamine, benzidine, o-toluidine, etc., substituted amines or amine salts containing alkyl, alkanol, alkarylor aryl radicals, such as methyl, ethyl, oxyethyl, cyanoethyl, butyl, propyl, benzyl and other radicals. As anions of above named amine the sulfates, chlorides, bromides, iodides, perchlorates, phosphates, chlorosulfonates, alkylsulfates, carboxylic acid anions, sulfonic acid anions, arylsulfonic acid anions and alkarylsulfonic acid anions may be mentioned. Specific examples include benzene sulfonic acid, benzene disulfonic acid, o-, mor p-toluene sulfonic acid, o-, mor p-ethylbenzene sulfonic acid, o-, mor p-cumene sulfonic acid, o-, mor p-tertiary amylbenzene sulfonic acid, 0-, mor p-hexyl benzene sulfonic acid, o-xylene-4-sulfonic acid, p-xylene-4-sulfonic acid, m-xylene-4- or 5-sulfonic acid, mesitylene-Z-sulfonic acid, durene-3-sulfonic acid, pentamethylbenzene sulfonic acid, o-dipropylbenzene4 sulfonic acid, alphaor beta-naphthalene sulfonic acid, o-, mor p-biphenyl sulfonic acid and alpha-, ethyl-betanaphthalene sulfonic acid, methane sulfonic acid, ethane sulfonic acid, lauryl sulfonic acid, methyl sulfuric acid, ethyl sulfuric acid, lauryl sulfuric acid, formic acid, acetic acid, propionic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, hexahydrobenzoic acid, nicotinic acid, oxalic acid, malonic acid, adipic acid, fumaric acid, tartaric acid, phthalic acid, phenylacetic acid, and the like. Among these anions, those which can be comparatively easly reduced at the cathode might be disadvantageous in hydrodimerization of acrylonitrile. In general, any kind of the aforesaid amines and anions can be combined with each other. Since the major industrial use of adiponitrile is the manufacturing of hexamethylenediamine which is a raw material of nylon, it is especially preferred for hydrodimerization reaction of acrylonitrile to use hexamethylenediamine or its substituted derivatives, such as halides, acetylides, or alkylated or cyanoethylated derivatives or their salts as an anion polymerization inhibitor.

The most preferred compounds as an anion polymerization inhibitor are sulfuric acid, hydrochloric acid, nitric acid, formic acid, acetic acid, ethanol, methanol, acetylene and its derivatives, methyl, ethyl, hexyl, lauryl and other alkylmercaptans, carbon monoxide, carbon dioxide, dimethylsulfide, carbon disulfide, benzene sulfonic acid, o-, mor p-toluene sulfonic acid, o-, mor p-ethylbenzene sulfonic acid, omor p-cumene sulfonic acid, o-, mor ptertiary amylbenzene sulfonic acid, o-, mor p-hexylbenzene sulfonic acid, o-xylene-4-sulfonic acid, p-xylene-4- sulfonic acid, m-xylene-4- or S-sulfonic acid, mesitylene- 2-sulfonic acid, durene-3-sulfonic acid, pentamethylbenzene sulfonic acid, o-dipropylbenzene-4-sulfonic acid, alphaor beta-naphthalene sulfonic acid, o-, mor p-biphenyl sulfonic acid and alpha-methyl-beta-naphthalene sulfonic acid and the aforesaid amines or amine salts derived from those amines and the acid anion aforementioned.

The concentration of the anion polymerization inhibitor in the aqueous phase of the emulsion is dependent on the type of inhibitor and may vary for example between 10 ppm. and 10%. The concentration of the anion polymerization inhibitor in the oil phase of the emulsion may vary between 0.01 and 10% by weight.

In forming the emulsion used for the electrolysis the components are set forth above may be added together or in any desired order.

As mentioned, the electrolysis may be effected in any conventional electrolytic cell, the acrylonitrile being hydrodimerized at a cathode potential of about --1.9 and 2.0 volt s.c.e. The supporting electrolyte salts, as mentioned, provide the necessary electric conductivity, but will not discharge at the cathode at this potential. The electrolysis may thus be effected by simply passing the electric current between the cathode and anode through the emulsion. It has been found preferable however, to utilize a cell having individual anode and cathode compartments separated by a diaphragm and utilizing a separate anolyte. As anolyte a mineral acid solution such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid in a concentration of less than 60% is preferred, with sulfuric acid being most satisfactory. It is also possible, however, to use organic acids, such as mono- =alkyl sulfuric acid, or aromatic or aliphatic sulfonic acids or in general any acid which will readily supply hydrogen ions consumed at the cathode. The anode may be of any material and preferably one which will not be corroded by oxygen, as for example, platinum, nickel, nickel cylicide, Duriiron, lead or lead alloys, such as lead-antimony alloy.

The diaphragm separating the anode compartment from the cathode compartment may be of conventional construction, as for example of sintered glass, porous sheet material, parchment paper, or the like. It is preferable however to use a cation exchange membrane as the diaphragm, as in this instance the hydroxyl ions generated at the cathode can be quantitatively neutralized by the hydrogen ions which selectively migrate through the cation exchange membrane from the anode compartment. A particularly suitable cation exchange membrane is one having sulfonic acid groups and carboxylic acid groups, as for example, a membrane formed of sulfonated styrenedivinyl-benzene type polymers. The cation exchange membrane may be of the homogeneous or heterogeneous type, and since with the use thereof the hydroxyl ions generated at the cathode can be neutralized quantitatively, the pH of the cathode compartment may be maintained at a constant value. It is desirable that during current flow the cation exchange membrane solely transfer the hydrogen ions and will not allow transfer of the other components, such as the sulfate ions, or acrylonitrile from the cathode compartment to the anode compartment. When the pH of the cathode compartment changes due to insufficient neutralization caused by a small quantity of the anion of the supporting electrolyte salt passing through the membrane and discharging electricity at the anode, the emulsion can be adjusted by adding acids, as for example, sulfuric acid or toluene sulfuric acid. As a cathode material having a high hydrogen over-voltage is preferred, as for example, copper, cadmium, lead, tin, mercury, or alloys of these metals. The emulsion which is subjected to the electrolysis is preferably circulated through the cathode and, as mentioned, may contain solvents such as acetonitrile, dioxane, ethylene glycol,

dimethyl formamide, dimethyl acetoamide, ethanol, or the like.

The electrolysis is preferably effected while maintaining the pH of the catholyte between about 1 and as when this value is exceeded, excessive bis-cyanoethyl ether formation occurs and when the pH becomes too low, hydrogen generation occurs at the cathode. The preferred pH is from 3 to 9 and in some cases it is desirable to maintain the catholyte almost neutral. It is preferable that the emulsion be supplied to the cathode with the oil phase finely dispersed and the cathode compartment should be so constructed as to favor the maintaining of as fine an emulsion as is possible. For this purpose it is desirable to construct the cathode compartment so that the emulsion may be forceably circulated against the cathode at a high velocity.

A horizontal cathode surface is generally no favorable due to problems of gas discharge and when multiple compartments are used, it is preferable to maintain spacers in each compartment in order that a fixed distance may be maintained in each compartment and turbulent flow facilitated. Spacers of the type which are conventionally used between ion exchange membranes in electrodiolysis equipment may be used. It is also preferable to circulate the anolyte through the anode compartment and flow velocities between 0.1 and 200 cm. per second, and preferably 5 to 100 cm. per second are preferable in both the anode and cathode compartments.

The electrolysis may be conducted at any temperature up to the boiling point of the acrylonitrile, though temperatures between 0 and 80 C. are preferred, with temperatures between and 18 C. being more preferable, and temperatures between room temperature and 70 C. being most preferable. The solubility of the acrylonitrile in the aqueous phase of the emulsion, of course, increases with increasing temperature.

If the temperature is too low, oligomers tend to be formed, and if too high, biscyanoethyl ether and propionitrile formation occurs. With increasing temperatures the resistance decreases, thus requiring a lower consumption of electric power. All these factors should be taken into consideration in determining optimum operating conditions.

The current density can vary widely, though densities between 3 and 30 amps. per dm. are preferred. Too low a current density should be avoided as the construction cost of the electrolysis cell thus increases while on the other hand at too high a current density the electrolysis voltage becomes high and the power consumption accordingly increases.

The adiponitrile produced by the electrolysis is mainly taken up in the oil phase of the emulsion and may be conveniently recovered. Thus, for example, the emulsion may be circulated out of the cathode compartment and separated into an oil phase and aqueous phase and the electrolysis product recovered from the separated phases and particularly the oil phase. A portion of the entire separated aqueous phase may be reconverted to an emulsion by addition of further acrylonitrile and recycled to the cathode compartment.

The separation of the emulsion, i.e. the breaking of the emulsion of the catholyte effluent may be effected by well known and conventional steps, as for example settling, centrifugal separation, filtration or the like, which may be facilitated by heating. The formed adiponitrile may then be recovered from the separated oil phase by such conventional modes as distillation, absorption, extraction, or the like. It is also possible, in accordance with the invention, to separate the majority of the acrylonitrile and adiponitrile by washing the oil phase with water in order to remove the supporting electrolyte salt and anion polymerization inhibitor. As mentioned, the invention allows the use of a substantially lower concentration of aqueous dissolved acrylonitrile than the prior known methods, and when operating with such lower concentrations of dissolved acrylonitrile, separation is greatly facilitated. With such lower concentrations it is possible to use supporting electrolyte salts which are comparatively weakly oleophilic and thus only dissolve in low concentration in the oil phase. The presence of the lower concentration of these salts in the oil phase facilitates extraction and allows the use of an extractor having a small number of theoretical stages. With the use of the low concentration of aqueous dissolved acrylonitrile which is possible in accordance with the invention, the relative ratio of formed adiponitrile to acrylonitrile in the oil phase correspondingly increases, thus facilitating the separation of the adiponitrile from the acrylonitrile. For example when operating in accordance with this mode, the amount of acrylonitrile to be separated from adiponitrile by distillation is relatively small, which facilitates the distillation operation and its economy. In general, where quaternary ammonium supporting electrolyte salts are used, salts having a total carbon number attached to the nitrogen of 10 or less, may be considered as weakly oleophilic and thus are preferred as the quaternary ammonium supporting electrolyte salts due to the fact that with the use thereof, the acrylonitrile will only dissolve in the aqueous phase in a relatively low concentration, which produces not only the advantages of separation and product recovery as just described, but also facilitates the efliciency and yield of the electrolysis itself. As mentioned, the most preferred salts are those which are incapable of increasing the solubility of the acrylonitrile to more than 10% by weight and most preferably those which will not allow dissolution of more than about 5% in the actual aqueous phase of the catholyte.

Where relatively high concentrations of aqueous dissolved acrylonitrile are used, as were required in the prior art methods, the separation becomes more cumbersome and difficult and may require multiple extraction procedures, or larger distillation plants and operating costs.

In general, when operating in accordance with the invention, with the use of the catholyte emulsion which contains the oil phase, a separate initial extraction procedure to initially separate the dissolved oil phase from the aqueous solution, is not required and the oil phase, as mentioned, may be easily separated. After this separation, extraction may be limited to a single step of removing the supporting electrolyte salt and the anion polymerization inhibitor from the separated oil phase which, as mentioned, may often be effected by a simple washing with water as, for example, in a column, using 00- or countercurrent flow procedure. The extraction of such salts can also be performed with solutions consisting mainly of water, but which may contain acrylonitrile, as, for example, in a concentration up to its saturation. Such extraction solutions may then be converted into the catholyte emulsion in accordance with the invention.

The electrolysis products may be fractionated into adiponitrile, propionitrile, the oligomer, and the like, after the removal of the supporting electrolyte salt. Acrylonitrile and adiponitrile may, of course, be separated from each other by such conventional processes as distillation.

The following examples are given by way of illustration, and not limitation:

EXAMPLE 1 The electrolysis cell used had lead cathode with a surface area of 10 cm. x 10 cm. and lead-antimony anode with the same area. The anode compartment and cathode compartment were partitioned by cation exchange membrane formed of a sulfonated divinyl benzene-styrenebutadiene copolymer of 1 mm. in thickness. The dimension of cathode compartment and anode compartment of the electrolysis cell were each 10 cm. in length, 10 cm. in width with 1 mm. distance between the electrode surface and membrane surface maintained by spacers. The anolyte was circulated by pump between anode compartment and anolyte tank, and emulsion for cathode compartment was also circulated by pump between cathode and catholyte 11 tank. As anolyte, a 2 N sulfuric acid solution was circulated at a flow rate of 30 cm./sec.

An emulsion consisting of 100 parts of a continuous aqueous phase and 50 parts of a dispersed oil phase was supplied to the cathode compartment and circulated at a flow rate of 30 cm./sec. The cell was operated at 40 C. with a current of 10 amperes.

The composition of the aqueous phase of emulsion supplied to the cathode was 3.5% of acrylonitrile, 9.5% of electrolysis product (8.9% of adiponitrile, .24% of propionitrile, a very small amount of biscyanoethyl ether and 0.31% of acrylonitrile oligomer) 69.0% of water. 15.0% of tetrapropyl ammonium sulfate and 3.5% of hexamethylene diamine p-toluene sulfonate. The pH was 3. The composition of oil phase was 23.7% of acrylonitrile, 64.2% of electrolysis products (60.5% of adiponitrile, 1.6% of propionitrile and 2.1% of acrylonitrile oligomer), 9% of water, 2% of tetrapropyl ammonium sulfate and 1% of hexamethylene diamine p-toluene sulfonate. The adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer present in the aqueous and oil phasm were not initially added, but were formed during operation and recirculated with the catholyte emulsion. During electrolysis, acrylonitrile was added to the efiluent emulsion of cathode compartment, and resultant homogenized emulsion was adjusted to the above composition and recirculated to the cathode compartment. The cell was operated in this manner for 300 hours. By the analysis of cathode emulsion during this period of operation, the percentage of selectivity of each product was obtained as a ratio of the weight of acrylonitrile consumed for each product to total amount of acrylonitrile consumed and was 2.5% for propionitrile, 94% for adiponitrile, 3.3% for acrylonitrile oligomer and 0.2% for biscyanoethyl ether. The effluent emulsion of cathode compartment was then discharged from the catholyte tank and settled to separate the oil phase. To separate the supporting electrolyte salt dissolved in this oil phase, the emulsion was to be passed through a continuous counter-current extraction column.

In this continuous-current extraction column, water was supplied dropwise from the top and oil phase was supplied from the bottom. By extracting the oil phase with an amount of water as small as one-fifth the amount of oil phase, it was possible to lower to less than 0.03% the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile is recovered by the distillation of oil phase material separated from supporting electrolyte salt.

When the emulsion containing acrylonitrile in the oil phase components was electrolyzed as in this example, even though the concentration of acrylonitrile in an aqueous phase was less than 5%, adiponitrile was formed at a high selectivity, and no polymer was formed in the electrolysis cell. The selectivity to propionitrile never increased over the long period of operation.

If, however, the example is repeated using an aqueous solution of acrylonitrile in a concentration less than 5% in place of the emulsion, acrylonitrile is converted exclusively into propionitrile and adiponitrile is not formed. Further, when an emulsion of acrylonitrile not containing the anion polymerization inhibitor used in this example is electrolyzed, a great amount of polymer is formed at the cathode in a short period of operation, and the acrylonitrile is converted to propionitrile, and the selectivity to adiponitrile progressively deq'reases with time, and electrolysis cannot be continued due to the formation of polymer. This is shown in Examples 1a and 1b.

EXAMPLE 1a In the same electrolysis in Example 1, the infiuent cathode solution was adjusted to the same composition for the aqueous phase, as was used in Example 1, except that neither oil phase was contained, nor hexamethylene diamine p-toluene sulfonate was added to the catholyte Cit 12 solution. Namely, a catholyte of aqueous acrylonitrile solution was prepared by adding acrylonitrile to the effluent of the cathode compartment and the oil phase was separated, and resultant aqueous solution phase alone was supplied to the cathode compartment.

Other conditions of the electrolysis were maintained the same as in Example 1, with the infiuent solution of cathode compartment being adjusted so that it had the following composition; 3.5% of acrylonitrile, 9.5% of the same electrolysis products consisting of adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer, 72.0% of water and 15% of tetrapropyl ammonium sulfate, having pH 3 and supplied to the cathode compartment at a flow velocity of 30 cm./sec. Electrolysis was conducted using an electric current of 10 amperes at a temperature of 40 C. The condition of the anode compartment was the same as in Example 1. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 91.7% for propionitrile, 8.0% for adiponitrile, 1.0% for oligomer and 0.2% for biscyanoethyl ether. When electrolysis was continued under the same conditions for 200 hours, polymer was deposited in the tachode compartment and the selectivity of propionitrile was gradually increased and that of adiponitrile decreased during electrolysis. Accordingly, it was not possible to keep operation of electrolysis stable under such conditions for a long period.

When the example was repeated, except that 3.5 of hexamethylene diamine p-toluene sulfonate was added to the cathode solution, the selectivity for propionitrile, adiponitrile and biscyanoethyl ether was almost the same, but no polymer was on the cathode and in the cathode compartment even after prolonged operation.

EXAMPLE lb Example 1 was repeated exactly, with the exception that hexamethylene diamine p-toluene sulfonate was not added to the emulsion supplied to the cathode compartment.

The catholyte emulsion consisted of parts of an aqueous solution and 30 parts of an oil phase. The composition of the aqueous phase of emulsion supplied to the cathode compartment was 3.5 of acrylonitrile, 9.5 of electrolysis products (adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer), 71.0% of water and 15.5% of tetrapropyl ammonium sulfate, and the pH was 3. The composition of the oil phase of the influent emulsion of cathode compartment was 23.7% of acrylonitrile, 64.2% of electro]ysis products( adiponitrile, propionitrile and acrylonitrile oligomer), 9% of water and 2.5% of tetrapropyl ammonium sulfate. In 40' hours of electrolysis, a very large amount of acrylonitrile polymer was formed, clogging the cell, and the electrolysis operation could no longer be continued. Of acrylonitrile consumed by electrolysis, 95.5% was converted to propionitrile and only 4.1% to adiponitrile.

EXAMPLE 10 Each of Examples 1, 1a and 1b were repeated at a pH of 7.6. In each case, similar results were obtained as in the corresponding example.

EXAMPLE 2 The equipment, including the electrolysis cell, of Example 1 was used. The anode solution was circulated under the same conditions as in Example 1. An emulsion consisting of 100 parts of the aqueous solution phase and 100 parts of the oil phase Was supplied to the cathode compartment, at a flow velocity of 50* cm./ sec. The composition of the aqueous phase of emulsion supplied to the cathode compartment was 2.0% of acrylonitrile, 5.7% of adiponitrile, 0.17% of propionitrile, a very small amount of biscyanoethyl ether, 0.14% of acrylonitrile oligomer, 71.9% of water, 17.0% of tetraethyl ammonium sulfate, 3.1% of N,N'-dimethylhexamethylene diamine paratoluene sulfonate, and 100 p.p.m. of methylcellulose, and

the pH was 8. The composition of the oil phase of the influent emulsion of the cathode compartment was 22.0% of acrylonitrile, 61% of adiponitrile, 1.8% of propionitrile, 0.1% of biscyanoethyl ether, 1.5% of acrylonitrile oligomer, 8% of water, 3% of tetraethyl ammonium sulfate and 2% of N,N-climethylhexamethylene diamine paratoluene sulfonate. Electrolysis was conducted in a current of 10 amperes and at a temperature of 55 C. The adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer in the catholyte influent were obtained from the efiluent from the cathode compartment by adding acrylonitrile to the effluent catholyte emulsion, adjusting to the aforesaid composition, and recirculating. The cell was operated for 300 hours. By the analysis of cathode emulsion in this period of operation, the percentage of selectively was 2.8% for propionitrile, 94.5% for adiponitrile, 2.3% for acrylonitrile oligomer and 0.2% for biscyanoethyl ether. The efiluent emulsion of cathode compartment was discharged from the catholyte tank and settled to separate the oil phase. To separate supporting electrolyte salt dissolved from the oil phase, it was sent through a continuous counter-current extracting tower.

In the continuous counter-current extracting tower, water was added dropwise from the top and the aforesaid oil phase was supplied from the bottom. The amount of supporting electrolyte salt contained in the oil phase was extracted to a value of less than 0.02%, using water in an amount of only one-tenth the amount of the oil phase.

Adiponitrile is recovered by distillation of the oil phase separated from supporting electrolyte salt.

When the emulsion containing acrylonitrile in an oil phase was electrolyzed in this way, even though the concentration of acrylonitrile in an aqueous solution was less than adiponitrile was formed at a high selectivity and polymer was not formed in the electrolysis cell, and selectivity of propionitrile never increased due to the polymer accumulation on the cathode, no matter how long the operation was continued. On the contrary, when the aqueous solution of acrylonitrile in the concentration of less than 5% was electrolyzed, it was shown that acrylonitrile is converted nearly exclusively into propionitrile and adiponitrile was not formed regardless of the presence of the anion inhibitor of N,N-dimethylhexamethylene p-toluene sulfonate. Further, when an emulsion of acrylonitrile not containing the anion polymerization inhibitor in this example was electrolyzed, a large amount of polymer was formed in the cathode compartment in a short period of operation, and consequently, acrylonitrile was converted into propionitrile due to the accumulation of polymer in the cathode and the selectivity of adiponitrile became low and electrolysis could not be continued due to the formation of polymer. The same results were obtained when the examples were repeated at a pH of 3.8.

EXAMPLE 3 The electrolysis cell of Example 1 was used and, as an anode solution, a 2-N sulfuric acid solution was circulated at a flow velocity of 30 cm./ sec.

An emulsion consisting of 50 parts of a continuous aqueous phase of 100 parts of a dispersed oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 40 C. at a current of 15 amperes.

The composition of the aqueous phase of emulsion supplied to the cathode compartment was 4% of acrylonitrile, 15.6% of adiponitrile, 0.7% of propionitrile, a very small amount of biscyanoethyl ether, 0.7% of acrylonitrile oligomer, 61.0% of water, 17.0% of tetraethyl ammonium p-toluene sulfonate and 1.0% of cyanoethylated hexamethylene diamine p-toluene sulfonate and the pH was 4.9. The composition of oil phase was 16.4% of acrylonitrile, 64.0% of adiponitrile, 2.8% of propionitrile, 2.8% of acrylonitrile oligomer, 7.0% of water, 4% of tetraethyl ammonium paratoluene sulfonate, and 3% of cyanoethylated hexamethylene diamine p-toluene sulfonate. The adiponitrile, propionitrile biscyanoethyl ether and acrylonitrile oligomer present in the emulsion were electrolysis products which were recirculated. During the electrolysis, acrylonitrile was added to the effluent emulsion of cathode compartment and resultant homogenized emulsion adjusted to the aforesaid composition was electrolyzed for 300 hours. By the analysis of cathode emulsion in this period of operation, the percentage of selectivity of each product was 4.0% for propionitrile, 92.0% for adiponitrile 4.0% for acrylonitrile oligomer and 0.1% for biscyanoether ether.

The eflluent emulsion of cathode compartment was discharged from the catholyte tank and settled to separate the oil phase. To separate the supporting electrolyte salt dissolved in this oil phase, a continuous counter-current extracting column was used.

In this continuous counter-current extracting column, Water was supplied dropwise from its top and oil phase was supplied from the bottom. By extracting the oil phase with an amount of water as small as one-fifth the amount of the oil phase, it was possible to lower to less than 0.03 the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile was recovered by the distillation of the treated oil phase.

When the emulsion containing acrylonitrile was electrolyzed as in this example, even though the concentration of acrylonitrile in an aqueous solution was less than 5%, adiponitrile was formed with a high selectivity and there was no polymer formation in the electrolysis cell, and the selectivity to propionitrile did not increase over the prolonged period of operation.

On the contrary, when an aqueous solution of acrylonitrile in a concentration less than 5% was electrolyzed,

the acrylonitrile was converted nearly exclusively into propionitrile and adiponitrile was not formed. Further, when an emulsion of acrylonitrile not containing the anion polymerization inhibitor was electrolyzed, a great amount of polymer was formed at the cathode; and after a short period of operation, the acrylonitrile was converted mainly to propionitrile and the electrolysis could not be continued. Changing the pH of the catholyte to 3.8 did not cause any substantial change in any of the results above noted. I

EXAMPLE 4 The electrolysis cell used was similar in type to that described in Example 1 and had, as the cathode, pure lead with a surface area of 10 cm. x 10 cm. and, as the anode, lead antimony alloy with the same surface area. The cell was 10 cm. in length, 10 cm. in width and 2 mm. in the distance between the cation exchange membrane and electrode.

In the electrolysis cell, an emulsion consisting of parts of continuous aqueous phase and 10 parts of oil phase was supplied at a flow velocity of 30 cm./ sec. and electrolyzed at 30 C. at a current of 10 amperes.

The composition of aqueous phase of emulsion supplied to the cathode compartment was. 3.1% of acrylonitrile, 4.9% of adiponitrile, 75.2% of water, 18.0% of tetraethyl ammonium sulfate and 3.5% of hexamethylene diamine paratoluene sulfonate, and its pH was 3. The composition of oil phase was 36% of acrylonitrile, 56.0% of adiponitrile, 6% of water, 1% of tetraethyl ammonium sulfate and 1% of hexamethylene diamine p-toluene sulfonate. During the electrolysis, the influent emulsion of cathode compartment was kept to the aforesaid composition and electrolysis was conducted for 6 hours. The selectively of propionitrile formed was 8.3%, and that of adiponitrile was 85.0%.

When the emulsion containing acrylonitrile in the oil phase components was electrolyzed as in this example, even though the concentration of acrylonitrile in an aqueous solution was less than 5%, adiponitrile was formed with a high selectivity and polymers were not formed, and

15 propionitrile selectivity never increased even after prolonged operation.

On the contrary, when an aqueous solution of acrylonitrile in a concentration less than Was electrolyzed, the acrylonitrile was converted nearly exclusively into propionitrile and adiponitrile was not formed in spite of the presence of the anion polymerization inhibitor. Further, when an emulsion of acrylonitrile not containing the anion polymerization inhibitor in this example was electrolyzed, a great amount of polymer was formed at the cathode in a short period of operation, increasing the propionitrile selectivity and finally preventing further operation.

EXAMPLE 5 The electrolysis cell of Example 1 was used, except the anode was platinum having a surface area of cm. x 10 cm. and the cathode was lead alloy containing 1% antimony which had the same surface area. As the anode solution, a 0.5-N sulfuric acid solution was circulated at a flow velocity of 40 cm./ sec.

The catholyte was an emulsion consisting of 100 parts of continuous aqueous phase and 50 parts of dispersed oil phase circulated at a flow velocity of cm./sec. and electrolyzed at 37 C. with a current of 10- amperes.

The composition of the aqueous phase of emulsion supplied to the cathode compartment was 2.5% of acrylonitrile, 8.5% of adiponitrile, 68.5% of water, 17.0% of tetraethyl ammonium sulfate and 3.5% of triethyl amine and triethyl amine naphthalene sulfonate having a pH of 8. The composition of oil phase of the influent emulsion of cathode was 20.3% of acrylonitrile, 62.2% of adiponitrile, 6.5% of water, 2.0% of tetraethyl ammonium ethylsulfate and 2.0% of triethyl amine and triethyl amine naphthalene sulfonate.

While keeping the influent emulsion of cathode compartment to the aforesaid composition, electrolysis was performed for 250 hours. According to the analysis of cathode emulsion, the percentage of selectivity was 4.9% for propionitrile, 90.0% for adiponitrile, 5.0% for acrylonitrile oligomer and 0.1% for biscyanoethyl ether.

When the emulsion containing acrylonitrile in the oil phase components was electrolyzed as in this example, even though the concentration of acrylonitrile in an aqueous solution was less than 5%, adiponitrile was formed at a high selectivity and polymers were not formed and the propionitrile selectivity did not increase even after prolonged operation.

EXAMPLE 6 The electrolysis cell of Example 1 was used, except the cathode was a lead-antimony alloy having a surface area of 10 cm. x 10 cm. and the anode was a leadantimony alloy having the same surface area. As anode solution, a l-N sulfuric acid solution was circulated at a flow velocity of cm./ sec.

The emulsion consisting of 100 parts of aqueous phase and 30 parts of oil phase was circulated at a flow velocity of 10 cm./sec. and electrolyzed at 50 C. with a current of 10 amperes.

The composition of the aqueous phase of the emulsion supplied to the cathode compartment was 3.1% of acrylonitrile, 4.1% of adiponitrile, 71.4% of water, 17.0% of trimethylethyl ammonium ethylsulfate and 3.5% of tributyl amine sulfate and its pH was 3. The composition of oil phase of influent emulsion in the cathode compartment was of acrylonitrile, 46% of adiponitrile, 6% of water, 3.0% of trimethylethyl ammonium sulfate and 1.0% of tributyl amine sulfate. While maintaining the above composition for the influent emulsion in the cathode compartment, electrolysis was continued for 24 hours. According to the analysis of operation, the percentage of selectivity was 13% for propionitrile, 83.0% for adiponitrile, 4.0% for acrylonitrile oligomer and 0.1% for biscyanoethyl ether.

16 When the emulsion containing acrylonitrile in the oil phase was electrolyzed as in this example, even though the concentration of acrylonitrile in an aqueous solution was less than 5%, adiponitrile was formed with a high selectivity and polymers were not formed and the propionitrile selectivity never increased.

EXAMPLE 7 The electrolysis cell of Example 1 was used, and as on anolyte, 0.5-N sulfuric acid solution was circulated at a flow velocity of 10 cm./sec.

An emulsion consisting of 50 parts of aqueous phase and parts of oil phase was supplied to the cathode compartment and circulated at a fiow velocity of 30 cm./sec. and electrolyzed at 40 C. with a current of 10 amperes. The composition of aqueous phase of the cathode emulsion was 4% of acrylonitrile, 11.8% of adiponitrile, 1.6% of propionitrile, a very small amount of bicycanoethyl ether, 0.6% of acrylonitrile oligomer, 61.0% of water, 18.0% of tetramethyl ammonium p-toluene, 2.5% of diethyl amine lauryl sulfate and 0.5% of alpha-naphthylamine p-toluene sulfonate and pH was 3. The composition of oil phase of the influent emulsion of cathode compartment was 20.0% of acrylonitrile, 58.0% of adiponitrile, 8.1% propionitrile, 2.8% of acrylonitrile oligomer, 6% of water, 3.0% of tetramethyl ammonium p-toluene sulfonate, 1.5% of dimethyl amine lauryl sulfate and 0.5 of alpha-naphthyl amine p-toluene sulfonate. The adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer both in the aqueous and oil phase were recirculated electrolysis products.

During the operation of electrolysis, the composition of influent emulsion of cathode was kept at the aforesaid value, and homogenized influent emulsion by adding acrylonitrile was electrolyzed for 24 hours. According to the analysis of the operation, the percentage of selectivity was 11.7% for propionitrile, 84.0% for adiponitrile, 4.1% for acrylonitrile oligomer and 0.2% for biscyanoethyl ether. The effluent emulsion of cathode was discharged from catholyte tank and settled to separate the oil phase. The supporting electrolyte salt dissolved in this oil phase was separated in a continuous counter-current extracting column.

In this continuous counter-current extracting column Water was supplied dropwise from its top and oil phase was supplied from the bottom. By extracting the oil phase with an amount of Water as small as one-fifth the amount of oil phase, it was possible to lower to less than 0.03% the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile was recovered by the distillation of the thus treated oil phase.

EXAMPLE 8 The same electrolysis cell as used in Example 1 was used and, as an anolyte solution, a 0.5-N sulfuric acid was supplied and circulated at a flow velocity of 30 cm./sec.

An emulsion consisting of 100 parts of aqueous phase and 50 parts of oil phase was circulated through the cathode compartment at a flow velocity of 20 cm./sec. and electrolyzed at 30 C. with a current of 10 amperes.

The composition of aqueous phase of cathode influent emulsion was 2% of acrylonitrile, 6% of adiponitrile, 70.5% of water, 11.0% of trimethylbenzyl ammonium sulfate and 2.5% of monomethyl amine acetate, and its pH was 3. The composition of oil phase of cathode influent emulsion was 22% of acrylonitrile, 60.0% of adiponitrile, 6% of water, 3.0% of trimethylbenzyl ammonium sulfate and 2.0% of monomethyl amine acetate.

While keeping the composition of infiuent emulsion of cathode compartment at aforementioned value, it was electrolyzed for 24 hours. According to the analysis of this operation the percentage of selectivity was 5.3%

EXAMPLE 9 The same electrolysis cell as was used in Example 1 was used and, as an anolyte, 0.9-N sulfuric acid solution was circulated at a flow velocity of 60 cm./sec.

An emulsion consisting of 100 parts of aqueous phase and 50 parts of oil phase was supplied to the cathode compartment and circulated at a flow velocity of 60 cm./-sec. and electrolyzed at 50 C. at a current of amperes.

The composition of aqueous phase of influent emulsion supplied to the cathode compartment was 4.0% of acrylonitrile, 12.7% of adiponitrile, 56.5% of water, 12.0% of methyltriethyl ammonium paratoluene sulfonate and 0.5% of N,N-dimethyl hexamethylene diamine lauryl sulfate and its pH was 4. The composition of oil phase of influence emulsion of cathode compartment was 18.7% of acrylonitrile, 59.4% of adiponitrile, 8% of water, 6% of methyltriethyl ammonium p-toluene sulfonate and 2% of N,N-demethyl hexamethylene diamine lauryl sulfate. While keeping the composition of influent emulsion of cathode compartment at the above value, the electrolysis was operated for hours. The percentage of selectivity was 3.3% for propionitrile, 91.0% for adiponitrile, 5.2% for acrylonitrile oligomer and 0.5 for biscyanoethyl ether.

EXAMPLE 10 The same electrolysis cell as was used in Example 1 was used and, as an anolyte, 1.0-N sulfuric acid solution was supplied and circulated at a flow velocity of 30 cm./sec.

An emulsion consisting of 100 parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 42 C. at a current of 10 amperes. The composition of aqueous phase of cathode influent emulsion was 3.5% of acrylonitrile, 4.1% of adiponitrile, 71.5% of water, 17.0% of tetraethyl ammonium sulfate and 3.5% of ammonium p-toluene sulfonate and its pH was 3. The composition oil phase of the cathode influent emulsion was 39% of acrylonitrile, 46.5% of adiponitrile, 6.1% of water, 2% of tetraethyl ammonium sulfate and 2% of ammonium p-toluene sulfonate. While maintaining the influent emulsion of the cathode compartment at the above composition, the electrolysis was continued for 24 hours. Selectivity was 3.5% for propionitrile, 91.3% for adiponitrile,

5.0% for acrylonitrile oligomer and 0.2% for biscyanoethyl ether.

EXAMPLE 11 The electrolysis cell of Example 1 was used and, as an anolyte, a 0.5-N sulfuric acid solution was circulated at a flow velocity of 30 cm./sec.

An emulsion consisting of 100 parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 50 cm./ sec. and electrolyzed at 40 C. at a current of 10 amperes.

The composition of aqueous phase of cathode influent emulsion was 4.5% of acrylonitrile, 10.1% of adiponitrile, 55.2% of water, 14.0% of tetraethyl ammonium paratoluene sulfonate and 0.2% of paratoluene sulfonic acid and its pH was 2.4. The composition of oil phase of the influent emulsion of cathode compartment was 24% of acrylonitrile, 54.7% of adiponitrile, 7% of water, 7% of tetraethyl ammonium paratoluene sulfonate and 0.1% of p-toluene sulfonate. While maintaining the influent emulsion of cathode compartment at the above composition, the electrolysis was continued for 24 hours. Analysis showed a selectivity of 5.3% for proionitrile, 88.2% for adiponitrile, 6.4% for acrylonitrile oligomer and 0.1% for biscyanoethyl ether.

The example is repeated using oxalic acid, acetic acid and sulfuric acid respectively in place of the p-toluene sulfonate and in each case adiponitrile is formed with high selectivity.

EXAMPLE 12 The electrolysis cell of Example 1 was used and, as an anode solution, a 1-N sulfuric acid solution was supplied and circulated at a flow velocity of 10 cm./sec.

An emulsion consisting of parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 60 cm./sec. and electrolyzed at 35 C. with a current of 10 amperes.

The composition of the aqueous phase of the emulsion supplied to the cathode compartment was 2.0% of acrylonitrile, 5.1% of adiponitrile, 75.0% of water, 17% of tetramethyl ammonium benzene sulfonate and 0.1% of carbon disulfide and its pH was 8. The composition of oil phase of cathode influent emulsion was 22.6% of acrylonitrile, 58.4% of adiponitrile, 6.5% of water, 3.0% of tetramethyl ammonium benzene sulfonate and 0.2% of carbon disulfide. While maintaining the composition of cathode influent emulsion at the above composition, electrolysis was continued for 24 hours. Analysis showed selectivity of 6.8% for propitonitrile, 86.0% for adiponitrile, 7.0% for acrylonitrile oligomer and 0.1% for biscyanoethyl ether.

When repeating the example using carbonylsulfide and carbon monoxide respectively in the place of carbondisulfide, adiponitrile will be formed from acrylonitrile with high selectivity.

EXAMPLE 13 The electrolysis cell had a lead. cathode with a surface area of 10 cm. x 10 cm. and a lead-antimony anode with the same area. The anode compartment and cathode compartment were partitioned by cation exchange membrane formed of sulfonated divinyl benzene-styrene-butadiene copolymer of 1 mm. in thickness. The dimensions of cathode compartment and anode compartment of the electrolysis cell were 10 cm. in length, 10 cm. in width and 1 mm. distance between the electrode surface and membrane surface. Spacers were inserted in each compartment so that this 1 mm. distance was easily kept. The anolyte was circulated by pump between anode compart ment and anolyte tank, and emulsion for cathode compartment was also circulated by pump between cathode and catholyte tank. As anolyte, a 2-N sulfuric acid solution was circulated at a flow rate of 30 cm./ sec.

An emulsion consisting of 100 parts of a continuous aqueous phase and 50 parts of a dispersed oil phase was supplied to the cathode compartment and circulated at a flow rate of 30 cm./sec. and electrolyzed at 50 C. with a current of 10 amperes. The composition of the aqueous phase of emulsion supplied to the cathode compartment was 11.5% of acrylonitrile, 9.0% of adiponitrile, 0.3% of propionitrile, 'a trace amount of bis-cyanoethylether, 0.2% of acrylonitrile oligomer, 65.0% of water, and 14.0% of tetraethylammonium p-toluene sulfonate. The pH was 7.1. The composition of the oil phase of the influent emulsion in the cathode compartment was 45% of acrylonitrile, 35.0% of adiponitrile, 1.1% of propionitrile, 0.9% of acrylonitrile oligomer, 9% of water, and 9% of tetraethylamrnonium p-toluene sulfonate. The adiponitrile, propionitrile, bis-cyanoethylether, and acrylonitrile oligomer present in the aqueous and oil phases in the influent emulsion were products formed during the electrolysis and thus present in the effluent emulsion. During the electrolysis, acrylonitrile was added to this eflluent etmulsion of cathode compartment, and resultant homogenized emulsion was adjusted to the above composition and re circulated to the cathode compartment. The cathode emulsion was analyzed over two hours of operation in the above manner. The percentage of selectivity of each product was calculated as a ratio of the weight of acrylonitrile consumed for each product to total amount of acrylonitrile consumed and was 3.0% for propionitrile, 94.3% for adiponitrile, 2.5% for acrylonitrile oligomer and 0.2% for biscyanoethyl ether. Then the efiiuent emulsion of cathode compartment was discharged from the catholyte tank and settled to separate the oil phase. To separate dissolved supporting electrolyte salt, the separated oil phase was passed through a continuous countercurrent extracting column.

In this continuous counter-current extracting column water was supplied dropwise from its top and the oil phase was supplied from the bottom. By extracting the oil phase using an amount of Water as small as one-tenth the amount of oil phase, it was possible to lower to less than 0.03% the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile was then recovered by distillation from the thus treated oil phase.

When the emulsion containing acrylonitrile in the oil phase components was electrolyzed as in this example, adiponitrile was formed at a high selectivity.

Operation was then continued in the same cell in the identical manner, except hexamethylene diamine p-toluene sulfonate was added by 2.0% to the emulsion, so that the emulsion recycled to the cathode compartment after the addition of acrylonitrile, consisted of 100 parts of aqueous phase of pH 7.1 and containing 11.5% of acrylonitrile, 9.0% of adiponitrile, 0.3% of propionitrile, a trace amount of bis-cyanoethylether, 0.2% of acrylonitrile oligomer, 63.0% of water, and 14.0% of tetraethylammonium p-toluene sulfonate and 50 parts of oil phase containing 44% of acrylonitrile, 34.5% of adiponitrile, 1.1% of propionitrile, 0.9% of acrylonitrile oligomer, 9% of water, 9% of tetraethylammonium p-toluene sulfonate and 1.5% hexamethylene diamine p-toluene sulfonate. Adiponitrile was obtained in the same yield, but operation could be continued for prolonged periods without interference by polymer formation.

When repeating the above electrolysis operations at a pH of 3.6 for the aqueous phase of the cathode emulsion, the same results were obtained.

EXAMPIJE 14 Electrolysis was carried out on the same electrolysis cell as in Example 13, except the cathode was made of cadmium, and 2 N sulfuric acid solution was circulated as the anolyte at a flow velocity of 30 cm./sec.

An emulsion consisting of 50 parts of a continuous aqueous phase and 100 parts of a dispersed oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 40 C. at a current of amperes.

The composition of the aqueous phase of emulsion supplied to the cathode compartment was 6% of acrylonitrile, 13.5% of adiponitrile, 0.4% of propionitrile, a very small amount of biscyanoethyl ether, 1.0% of acrylonitrile oligomer, 61.1% of water, 14.5% of tetraethyl ammonium p-toluene sulfonate, 0.03% of methyl cellulose and 3.5% of dimethyl hexamethylene diamine p-toluene sulfonate and the pH was 3. The composition of oil phase was 24.6% of acrylonitrile, 55.3% of adiponitrile, 1.8% of propionitrile, 4.0% of acrylonitrile oligomer, 7% of Water, 6% of tetraethyl ammonium p-toluene sulfonate and 1% of dimethyl hexamethylene diamine p-toluene sulfonate. The adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer present in the aqueous and oil phases were electrolysis products which were recirculated from the effluent emulsion of cathode compartment. During the electrolysis, acrylonitrile was added to this efliuent emulsion of cathode compartment and resultant homogenized emulsion adjusted to the aforesaid composition. The electrolysis was conducted for 200 hours. By the analysis of cathode emulsion over this period of operation, the percentage of selectivity of each product was 3.0% for propionitrile, 90.3% for adiponitrile, 6.5% for acrylonitrile oligomer and 0.2% for hiscyanoethyl ether.

The eflluent emulsion of compartment was discharged from the catholyte tank and settled to separate the oil phase.

To separate dissolved supporting electrolyte salt the separated oil phase was treated in a continuous counter current extracting column.

In this continuous counter-current extracting column water was supplied dropwise from its top and the oil phase was supplied from the bottom. By extracting the oil phase with an amount of water as small as one-eighth the amount of oil phase, it was possible to lower to less than 0.03 the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile was recovered by the distillation of the thus treated oil phase.

When acrylonitrile emulsion containing polymerization inhibitor in an aqueous solution was thus electrolyzed, adiponitrile was formed at a high selectivity and polymers were not formed at all in the electrolysis cell and the selectivity of propionitrile never increased due to the accumulation of polymer at the cathode, no matter how long the operation was continued.

EXAMPLE 15 The electrolysis cell had, as the cathode, pure lead with a surface area of 10 cm. x 10 cm. and, as the anode, lead antimony alloy with the same surface area. The cell was 10 cm. in length, 10 cm. in width and 2 mm. in the distance between the diaphragm and electrodes.

In the electrolysis cell, an emulsion consisting of parts of aqueous solution and 10 parts of the oil phase was supplied at a flow velocity of 30 cm./sec. and electrolyzed at 50 C. at a current of 10 amperes.

The composition of aqueous phase of emulsion supplied to the cathode compartment was 6.1% of acrylonitrile, 11.5 of adiponitrile, 0.7% of propionitrile, a very small amount of bis-cyanoethyl ether, 0.8% of acrylonitrile oligomer, 57.4% of water, 12.0% of tetraethylammonium p-toluene sulfonate and 1.0% of hexamethylene diamine p-toluene sulfonate, and its pH was 3. The composition of the oil phase portion was 27.0% of acrylonitrile, 50.0% of adiponitrile, 3.1% of propionitrile, 3.3% of acrylonitrile oligomer, 8% of water, 7% of tetraethylammonium p-toluene sulfonate, and 1% of hexamethylene diamine p-toluene sulfonate. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 5.5% for propionitrile, 88.0% for adiponitrile, 5.9% for acrylonitrile, 5.9% for acrylonitrile oligomer, and 0.6% for hiscyanoethylether.

EXAMPLE 16 The electrolysis cell of Example 13 was used and 1.2-N sulfuric acid solution as the anolyte was circulated at a flow velocity of 30 cm./sec.

An emulsion consisting of 100 parts of aqueous phase and 20 parts of oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 5 0 C. with a current of 10 amperes.

The composition of the aqueous phase of emulsion supplied to the cathode compartment was 6.0% of acrylonitrile, 2.0% of adiponitrile, 0.06% of propionitrile, a very small amount of bis-cyanoethylether, 0.08% of acrylonitrile oligomer, 17.0% of tetraethylammonium sulfate and 3.5% of triethylamine naphthalene sulfonate, and its pH was 3. The composition of the oil phase of emulsion was 66% of acrylonitrile, 21.4% of adiponitrile, 0.7% of propionitrile, 0.9% of acrylonitrile oligomer, 7% of water, 2% of tetraethylammonium sulfate, and 2% of triethylamine naphthalene sulfonate. The adiponitrile, propionitrile, bis-cyanoethylether, and acrylonitrile oligomer present in the aqueous and oil phases were recirculated electrolysis products.

During electrolysis, acrylonitrile was added to the cffluent emulsion of the cathode compartment and resultant homogenized emulsion was adjusted to the aforesaid composition, and was supplied to the cathode compartment to be electrolyzed for 300 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 3.0% for propionitrile, 92.8% for adiponitrile, 4.0% for acrylonitrile oligomer, and 0.2% for bis-cyanoethylether. Then the efiluent emulsion in the cathode compartment was removed from the catholyte tank and settled to separate the oil phase therefrom. To separate supporting electrolyte salt dissolved in the oil phase, it was passed through a continuous counter-current extracting tower.

At the continuous counter-current extracting tower, water was added dropwise from the top and the aforesaid oil phase was supplied from the bottom. The amount of supporting electrolyte salt contained in the oil phase was extracted to less than 0.03% with an amount of water of only one-tenth the amount of the oil phase.

Adiponitrile was recovered by distillation of the treated oil phase.

EXAMPLE 17 The electrolysis cell of Example 13 was used, and as an anolyte, 0.5-N sulfuric acid solution was circulated at a flow velocity of 30 cm./ sec.

An emulsion consisting of 100 parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 60 C. with a current of amperes.

The composition of the aqueous phase of emulsion supplied to the cathode compartment was 8.5% of acrylonitrile, 9.4% of adiponitrile, 0.45% of propionitrile, a very small amount of bis-cyanoethyl ether, 0.68% of acrylonitrile oligomer, 61.0% of water, 17.0% of tetraethylammonium ethylsulfate, and 3.0% of monoethylamine acetate, and its pH was 7.1. The composition of the oil phase of emulsion was 40% of acrylonitrile, 44% of adiponitrile, 2.1% of propionitrile, 2.7% of acrylonitrile oligomer, 7% of water, 3% of tetraethylammonium ethylsulfate, and 1% of monoethylamine acetate. The adiponitrile, propionitrile, bis-cyanoethyl ether, and acrylonitrile oligomer in the aqueous phase and oil phase were recirculated electrolysis products.

During the operation of electrolysis, the composition of influent emulsion of cathode was kept at the aforesaid value, and homogenized influent emulsion by adding acrylonitrile was electrolyzed for 100 hours. Analysis showed selectivity of 4.3% for propionitrile, 89.7% for adiponitrile, 5.5% for acrylonitrile oligomer and 0.5% for biscyanoethyl ether. The effluent emulsion of cathode was discharged from the catholyte tank and settled to separate the oil phase. To separate supporting electrolyte salt dissolved in this oil phase, the oil phase was treated in a continuous counter-current extracting column.

In this continuous counter-current extracting column water was supplied dropwise from its top and oil phase was supplied from the bottom. By extracting the oil phase with water in an amount of as small as one-tenth the amount of oil phase, it was possible to lower to less than 0.03% the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile was recovered by the distillation of the thus treated oil phase.

In the electrolysis of such an emulsion as containing the oil phase of acrylonitrile and not containing any anion polymerization inhibitors, it was desirable to clean the electrolysis cell after a period of operation.

When electrolysis was performed under the same conditions as in this example, except the COS, CO, and acetylene compounds respectively were used as the anion polymerization inhibitors, adiponitrile could be formed in a high yield from acrylonitrile without the formation of polymer.

EXAMPLE 18 The electrolysis cell of Example 13 was used, except the cathode was made of 1ead-antimony alloy instead of lead and, as the anolyte, 0.5-N sulfuric acid solution was circulated at a flow rate of 30 cm./sec.

An emulsion consisting of parts of an aqueous solution and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow rate of 30 cm./sec., and electrolyzed at 50 C. with a current of 10 amperes.

The composition of the aqueous phase of the emulsion supplied to the cathode compartment was 2% of acrylonitrile, 6% of electrolysis product (containing 5.7% of adiponitrile, 0.2% of propionitrile, a trace amount of bis-cyanoethylether, and 0.2% of acrylonitrile oligomer), 71.5% of water, 17.0% of tetraethylammonium sulfate, and 3.5% of cyanoethylated hexamethylenediamine ptoluene sulfonate, and its pH was 3. The composition of the oil phase portion was 22% of acrylonitrile, 66% of electrolysis product (consisting of 62.1% of adiponitrile, 1.2% of propionitrile and 1.7% of acrylonitrile oligomer), 7% of water, 3.0% of tetraethylammonium sulfate, and 2% of cyanoethylated hexamethylene diamine p-toluene sulfonate. The adiponitrile, propionitrile, biscyanoethyl ether, and acrylonitrile oligomer in the aqueous and oil phases constituted electrolysis products.

During the electrolysis, acrylonitrile was added to the efiiuent emulsion of cathode compartment, and the resultant emulsion was adjusted to the aforesaid composition and homogenized. Electrolysis was operated for 300 hours. Analysis of cathode emulsion during this period of operation showed selectivity of 3.3% for propionitrile, 94.0% for adiponitrile, 2.5% for acrylonitrile oligomer and 0.2% for bis-cyanoethyl ether. The efliuent emulsion of cathode compartment was discharged from the catholyte tank and settled to separate the oil phase. Electrolyte salt dissolved in the oil phase was removed in a continuous countercurrent extracting tower.

At the continuous counter-current extracting tower, water was added dropwise from the top and the aforesaid oil phase was supplied from the bottom. The amount of supporting electrolyte salt contained in the oil phase was exartcted to less than 0.03% with an amount of water of only one-sixth the amount of the oil phase.

Adiponitrile was recovered by distillation of the treated oil phase.

EXAMPLE 18a Example 18 was repeated, except hexamethylene diamine p-toluene sulfonate was not added, and as the catholyte an aqueous acrylonitrile solution was used which was prepared by adding acrylonitrile to the effiuent of the cathode compartment after separation of the oil phase. The catholyte was thus a homogeneous aqueous solution rather than an emulsion. The other conditions of the electrolysis were maintained same as in EX- ample 18. The influent solution of the cathode compartment was adjusted so that it contained 6% of the electrolysis product (consisting of acrylonitrile, adiponitrile, propionitrile, bis-cyanoethyl ether and acrylonitrile oligomer), 75% of water and 15% of tetrapropyl ammonium sulfate, and had a pH of 3 and was supplied to the cathode compartment at a flow velocity of 30 cm./ sec. The electrolysis was conducted with an electric current of 10 amperes at a temperature of 50 C. The anode was operated in an identical manner as Example 18. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 91.8% for propionitrile, 8.0% for adiponitrile, 1.0% for oligomer and 0.2% for bis-cyanoethyl ether. When the electrolysis was continued under the same conditions for 200 hours, polymer was deposited in the cathode compartment and the selectivity of propionitrile was gradually increased and that of adiponitrile decreased during electrolysis. Accordingly, it was not possible to keep operation of the electrolysis stable under such conditions for a long period.

When however 3.5% of cyanoet'hylated hexamethylene diamine p-toluene sulfonate was added to the catholyte solution, no polymer was formed on the cathode and in the cathode compartment even after prolonged operation.

'EXAMPLE 18b Example 18 was repeated except that hexamethylene diamine p-toluene sulfonate was not added to the emulsion supplied to the cathode compartment.

The composition of the aqueous phase of emulsion supplied to the cathode compartment was thus 2% of acrylonitrile, 6% of electrolysis products (adiponitrile, propionitrile, bis-cyanoethyl ether and acrylonitrile oligomer), 75% of water and 17.0% of tetraethyl ammonium sulfate, and the composition of oil phase was thus 22% of acrylonitrile, 66% of electrolysis products (adiponitrile, propionitrile and acrylonitrile oligomer), 7% of water and of tetraethyl ammonium sulfate. In 40 hours of electrolysis, a very large amount of acrylonitrile polymer was formed. Of acrylonitrile consumed by electrolysis, 95.5% was converted to propionitrile and only 4.1% to adiponitrile.

EXAMPLE 19 The electrolysis cell of Example 13 was used and 2-N sulfuric acid was circulated as the anolyte at a flow velocity of 30 cm./ sec.

An emulsion consisting of 100 parts of an aqueous phase and.50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 35 C. with a current of 10 amperes.

The composition of the aqueous phase of the emulsion supplied to the cathode compartment was 4% of acrylonitrile, 10.2% of adiponitrile, 1.1% of propionitrile, a very small amount of bis-cyanoethylether, 0.7% of acrylonitrile oligomer, 63.0% of water, 18.0% of tetramethylammonium p-toluene sulfonate, 3.0% of dimethylamine lauryl sulfate, and 0.1% of ot-naphthylamine and its pH was 3. The composition of the oil phase was 22.0% of acrylonitrile, 56.0% of adiponitrile, 6.2% of propionitrile, 3.6% of acrylonitrile oligomer, 6% of water, 4% of tetraethylammonium p-toluene sulfonate, 2% of dimethylamine lauryl uslfate and 0.3% a-naphthylamine. The adiponitrile, propionitrile, bis-cyanoethylether, and acrylonitrile oligomer were electrolysis products.

During the electrolysis, acrylonitrile was added to the effluent emulsion of the cathode compartment, and the resultant emulsion was adjusted to the aforesaid composition and homogenized. The electrolysis was conducted for 24 hours. Analysis of cathode emulsion over this period of operation showed a selectivity of 9.4% for propionitrile, 85.0% for adiponitrile, 5.5% for acrylonitrile oligomer and 0.1% for bis-cyanoethyl ether. The efiluent emulsion of the cathode compartment was discharged from the catholyte tank and settled to separate the oil phase. To separate supporting electrolyte salt dissolved in the oil phase, the oil phase was passed through a continuous counter-current extracting tower.

At the continuous counter-current extracting tower, water was added dropwise from the top and the aforesaid oil phase was supplied from the bottom. The amount of supporting electrolyte salt contained in the oil phase was extracted to less than 0.03% using water in an amount of only one-eighth the amount of the oil phase.

Adiponitrile was recovered by distillation of the treated oil phase.

EXAMPLE The electrolysis cell of Example 13 was used with a l-N sulfuric acid circulated at a flow velocity of cm./ sec. as the anolyte.

An emulsion consisting of 100 parts of aqueous phase and 50 parts of oil phase was used as the catholyte and circulated at a flow velocity of 30 cm./ sec. and electrolyzed at C. with a current of 10 amperes.

The composition of aqueous phase of cathode influent emulsion was 4% of acrylonitrile, 10.1% of adiponitrile,

0.3% of propionitrile, a vow small amount of bis-cyanoethylether, 0.3% of acrylonitrile oligomer, 66.8% of water, 17.0% of tetrapropylammonium sulfate, and 3.5% of ammonium benzene sulfonate, and its pH was 7.5. The composition of the oil phase of emulsion was 24% of acrylonitrile, 59% of adiponitrile, 1.9% of propionitrile, 17% of acrylonitrile oligomer, 9% of water, 2% of tetrapropylammonium sulfate and 1% of ammonium p-toluene sulfonate. The adiponitrile, propionitrile, bis-cyanoethylether, and acrylonitrile oligomer in the aqueous and oil phase where recirculated electrolysis products.

During the operation of electrolysis, the composition of infiuent emulsion of the cathode was kept at the aforesaid value by adding acrylonitrile and was electrolyzed for 24 hours. Analysis showed a selectivity of 3.0% for propionitrile, 92.0% for adiponitrile, 2.6% for acrylonitrile oligomer and 0.2% for bis-cyanoethylether. The efiluent emulsion of the cathode was discharged from the catholyte tank and settled to separate the oil phase, and further treated in the manner described in Example 18.

EXAMPLE 21 The electrolysis cell of Example 13 was used and, as anolyte solution, a 2-N sulfuric acid was supplied and circulated at a flow velocity of 30 cm./sec.

To the cathode compartment, an emulsion consisting of 100 parts of aqueous phase and parts of oil phase was supplied and circulated at a flow velocity of 50 cm./sec. and electrolyzed at 30 C. with a current of 10 amperes.

The composition of aqueous phase of cathode infiuent emulsion was 2.0% of acrylonitrile, 6.0% of adiponitrile, 74.7% of water, 17.0% of tetraethylammonium sulfate, and the balance of carbon disulfide, and its pH was 3. The composition of the oil phase of emulsion was 22% of acrylonitrile, 64.6% of adiponitrile, 6.5% of water, 2.1% of tet-raethylammonium sulfate, and 6.3% carbon disulfide.

The electrolysis was continued for 3 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 3.3% for propionitrile, 93.6% for adiponitrile, 2.7% for acrylonitrile oligomer, and 0.2% of biscyanoethylether.

When the electrolysis was performed under the same conditions, except that COS, CO, and acetylene compounds were used in place of carbon disulfide, adiponitrile was also formed at a high yield from acrylonitrile without the formation of polymer.

EXAMPLE 22 The electrolysis cell of Example 13 was used and, as an anolyte, a 0.5-N sulfuric acid solution was supplied and circulated at a flow velocity of 30 cm./ sec.

An emulsion consisting of 100 parts of an aqueous phase of the following composition and 50* parts of an oil phase of the following composition was supplied to the cathode compartment and circulated at a flow velocity of cm./sec. and electrolyzed at 40 C. at a current of 10 amperes. The composition of the aqueous phase of cathode infiuent emulsion was 4% of acrylonitrile, 4.4% of adiponitrile, 0.6% of propionitrile, 0.2% of oligomer, and 55.6% of water, 35.0% of tetramethylammonium methylsulfate and 0.2% of p-toluene sulfonate, and its pH was 2.4. The composition of the oil phase of emulsion was 40% of acrylonitrile, 44% of adiponitrile, 6% of water, 2.0% of tetramethylammonium sulfate, and 0.1% of p-toluene sulfonate.

The electrolysis was continued for 4 hours. In terms of acrylonitrile consumed by the electrolysis, the percentage of selectivity was 11.4% for propionitrile, 85.0%, for adiponitrile, 3.5% for acrylonitrile oligomer, and 0.1% for bis-cyanoethylether.

When the electrolysis is performed under the same conditions as in this example except oxalic acid and sulfuric acid are used, respectively, in place of the p-toluene sulfonate, adiponitrile will be obtained in a high yield, and polymer will not form.

EXAMPLE 23 The cell of Example 13 was used and, as an anolyte, a 2-N sulfuric acid solution was circulated at a flow velocity of 30 cm./sec.

An emulsion consisting of 100 parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a How velocity of 60 c1n./sec. and electrolyzed at 40 C. at a current of 5 amperes.

The composition of aqueous phase of cathode infiuent emulsion was 4% of acrylonitrile, 15.2% of adiponitrile, 0.7% of propionitrile, a trace amount of bis-cyanoethylether, 1.0% of acrylonitrile oligomer, 68.0% of water, and 18.0% of tetraethylammonium p-toluene sulfonate, and its pH was 8. The composition of the oil phase of emulsion was 17.0% of acrylonitrile, 64.0% of adiponitrile, 3.1% of propionitrile, 4.3 of acrylonitrile oligomer, 6% of water, and 5.5% of tetraethylammonium ptoluene sulfonate. The adiponitrile, propionitrile, bis.- cyanoethyl ether, and acrylonitrile oligomer were recirculated electrolysis products.

During the operation of electrolysis, the composition of influent emulsion of cathode was kept at the aforesaid value by adding acrylonitrile and was electrolyzed for 10 hours. Analysis showed that selectivity was 4.3% for propionitrile, 89.5% for adiponitrile, 6.0% for acrylonitrile oligomer and 0.2% for bis-cyanoethyl ether. The effluent emulsion of cathode was discharged from catholyte tank and settled to separate the oil phase. To separate supporting electrolyte salt dissolved in this oil phase, a continuous counter-current extracting column was used.

In this continuous counter-current extracting column, water was supplied dropwise from its top, and the oil phase was supplied from the bottom. By extracting the oil phase with water in an amount as small as oneeighth the amount of oil phase, it was possible to lower to less than 0.03% the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile was recovered by the distillation of the thus treated oil phase.

EXAMPLE 24 The electrolysis cell of Example 13 was used and, as an anolyte solution, a 0.5-N sulfuric acid solution was supplied and circulated at a flow velocity of 10 cm./sec.

An emulsion consisting of 100 parts of an aqueous phase and 50 parts of oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./ sec. and electrolyzed at 50 C. with a current of 15 amperes.

The composition of the aqueous phase of emulsion supplied to the cathode compartment was 4.5% of acrylonitrile, 7.5% of adiponitrile, 77.0% of water, and 11.0% of potassium benzene sulfonate, and its pH was 3. The composition of the oil phase of emulsion was 34% of acrylonitrile, 57% of adiponitrile, 6% of water and 3% of potassium benzene sulfonate. The emulsion was electrolyzed and recirculated to the cathode compartment for 10 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 9.3% for propionitrile, 80.5% for adiponitrile, 10.1% for acrylonitrile oligomer and 0.1% for bis-cyanoethyl ether. The same result Was obtained when ammonium benzene sulfonate was used in place of potassium benzene sulfonate in this example.

EXAMPLE The electrolysis cell of Example 13 was used and, as an anolyte solution, a 0.5-N sulfuric acid was supplied and circulated at a flow velocity of cm./sec.

To the cathode compartment, an emulsion consisting of 100 parts of an aqueous phase and parts of an oil phase was supplied and circulated at a flow velocity of 50 cm./sec. and electrolyzed at 40 C. at a current of 5 amperes.

The composition of aqueous phase of influent emulsion supplied to the cathode compartment was 2% of acrylonitrile, 2% of adiponitrile, 86.0% of water and 10.0% of lithium chloride, and its pH was 3. The composition of the oil phase of emulsion was 48.0% of acrylonitrile, 35.0% of adiponitrile, 5% of water, and 0.2% of lithium chloride. The electrolysis was carried out for 6 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 18.3% for propionitrile, 74.0% for adiponitrile, 7.5 for acrylonitrile oligomer, and 0.1% for biscyanoethyl ether.

EXAMPLE 26 An electrolysis cell which had a lead cathode with a surface area of 10 cm. x 10 cm. and a lead-antimony anode with the same area was used. The anode compartment and cathode compartment of the cell were partitioned by cation exchange membrane formed of sulfonated divinyl benzene-styrene-butadiene copolymer of 1 mm. in thickness. The dimension of cathode compartment and anode compartmnet of the electrolysis cell were 10 cm. in length, 10 cm. in width and 1 mm. distance between the electrode surface and membrane surface maintained by spacers. The anolyte was circulated by pump between anode compartment and anolyte tank, and the catholyte was also circulated by pump between cathode and catholyte tank. As anolyte solution, l-N sulfuric acid solution was circulated at a flow velocity of 10 cm./sec.

An emulsion consisting of parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 40 C. with a current of 10 amperes.

The composition of the aqueous phase of the emulsion supplied to the cathode compartment was 2% of acrylonitrile, 5.1% of adiponitrile, 0.6% of propionitrile, a very small amount of bis-cyanoethyl ether, 0.15% of acrylonitrile oligomer, 71.4% of water, 17.0% of tetramethyl ammonium-sulfate, 3.5% of triethylamine and triethylamine benzenesulfonate and its pH was 8. The composition of the oil phase was 23% of acrylonitrile, 58.9% of adiponitrile, 7.7% of propionitrile, 1.7% of acrylontrile oligomer, 6% of water, 2% of tetramethyl ammonium sulphate, 1% of triethylamine and triethylamine benezenesulfonate. The adiponitrile, propionitrile, bis-cyanoethyl ether, and acrylonitrile oligomer were recirculated electrolysis products. During electrolysis, acrylonitrile was added to the efiiuent emulsion of cathode compartment, and resultant emulsion was adjusted to the aforesaid composition and homogenized. The electrolysis was operated for 300 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 11.3% for propionitrile, 86.0% for adiponitrile, 2.5% for acrylonitrile oligomer and 0.1% for bis-cyanoethyl ether. The efiiuent emulsion of cathode compartment was discharged from the catholyte tank and settled to separate the oil phase. To separate supporting electrolyte salt dissolved from the oil phase, it was passed through a continuous counter-current extracting tower.

At the continuous counter-current extractinig tower, water was added dropwise from the top and the aforesaid oil phase was supplied from the bottom. The amount of supporting electrolyte salt contained in the oil phase was extracted to less than 0.03% using water in an amount of only one-tenth the amount of the oil phase.

Adiponitrile was recovered by distillation of the treated oil phase.

EXAMPLE 27 The electrolysis cell of Example 26 was used and, as an anolyte solution, a 6.5-N sulfuric acid was supplied and circulated at a flow velocity of 30 cm./sec.

To the cathode compartment, an emulsion consisting of 100 parts of an aqueous phase and 50 parts of an oil phase was supplied and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 40 C. with a current of amperes.

The aqueous phase of the emulsion supplied to the cathode had a composition of 4.5% of acrylonitrile, 7.5% of adiponitrile, 77.5% of water, 11.0% of potassium benzene sulfonate, and 3.5% of hexamethylenediamine ptoluene sulfonate, and its pH was 3. The oil phase had a composition of 33% of acrylonitrile, 55% of adiponitrile, 3% of potassium benzene sulfonate, 2% of hexamethylenediamine p-toluene sulfonate, and 7% of water.

The electrolysis was continued for 10 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity for each product was 9.3% for propionitrile, 80.5% for adiponitrile, 10.1% for acrylonitrile oligomer, and 0.1% for bis-cyanoethyl ether.

EXAMPLE 28 The electrolysis cell as in Example 27 was used and, as an anolyte, 0.5-N sulfuric acid solution was circulated at a flow velocity of 30 cm./ sec.

An emulsion consisting of 100 parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at C. at a current of 10 amperes.

The composition of the aqueous phase of the emulsion supplied to the cathode compartment was 4% of acrylonitrile, 3.5% of adiponitrile, 71.5% of water, 17.0% of tetraethylammonium chloride, and 3.5% of hexamethylenediamine p-toluene sulfonate, and its pH was 7. The composition of the oil phase was 45.5% of acrylonitrile, 40.0% of adiponitrile, 6% of water, 1.1% of lithium chloride, and 1.1% of hexamethylenediamine sulfonate. The electrolysis was continued for six hours. Then, in terms of acrylonitrile consumed by electrolysis, the percentage of selectivity for each electrolysis product was 3.0% for propionitrile, 89.0% for adiponitrile, 7.9% for acrylonitrile oligomer, and 0.1% for biscyanoethyl ether.

EXAMPLE 29 The electrolysis cell of Example 26 was used and, as an anolyte, a 1-N sulfuric acid solution was supplied and circulated at a flow velocity of 30 cm./ sec.

An emulsion consisting of 100 parts of an aqueous phase and parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 50 C. at a current of 10 amperes.

The aqueous phase of the emulsion supplied to the cathode was composed of 2% of acrylonitrile, 5.4% of adiponitrile, 74.7% of water, 17.0% of tetraethylammonium sulfate and 0.3% of carbon disulfide, and had a pH of 3. The oil phase was composed of 22.7% of acrylonitrile, 63.5% of adiponitrile, 7% of water, 21% of ethylammonium sulfate, and 0.3% of carbon disulfide. The electrolysis was continued for 3 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity for the electrolysis product was 3.3% for propionitrile, 93.6% adiponitrile, 2.9% for acrylonitrile oligomer, and 0.2% for bis-cyanoethyl ether.

When anion polymerization inhibitors such as p-toluene sulfonate, COS, CO and acetylene compounds are used in lieu of the carbon disulfide, adiponitrile will be obtained in a high yield.

EXAMPLE 30 The electrolysis cell of Example 26 was used. As anolyte, a 1-N sulfuric acid solution Was circulated at the flow velocity of 20 cm./ sec. An emulsion comprising 50 parts of aqueous solution and 50 parts of an oil phase was supplied to the cathode compartment, and circulated at the flow velocity of 30 cm./sec. The electrolysis was 28 carried out at a current of 20 amp. and at the temperature of 40 C.

The composition of the aqueous phase of the emulsion supplied to the cathode compartment was 6.0% of acrylonitrile, 10.7% of adipontrile, 0.9% of propionitrile, a trace amount of bis-cyanoethyl ether, 0.4% of acrylonitrile oligomer, 61.5% of water, 18.0% of tetramethyl ammonium p-toluene sulfonate, and 2.5% of monomethylamine acetate, and its pH was 8. The composition of the oil phase was 29.0% of acrylonitrile, 52.8% of adiponitrile, 4.6% of propionitrile, 1.8% of acrylonitrile oligomer, 6% of water, 4% of tetramethyl ammonium p-toluene sulfonate, and 1% of monomethylamine acetate. The adiponitrile, propionitrile, bis-cyanoethyl ether and acrylonitrile oligomer were recirculated electrolysis products. During electrolysis, acrylonitrile was added to the efiluent emulsion of the cathode compartment, and the resultant emulsion was adjusted to the aforesaid composition and homogenized. The electrolysis was operated for 200 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 7.8% for propionitrile, 89.0% for adiponitrile, 3.0% for acrylonitrile oligomer, and 0.2% for bis-cyanoethyl ether. The eflluent emulsion of the cathode compartment was discharged from the catholyte tank and settled to separate the oil phase. To separate supporting electrolyte salt dissolved in this oil phase, it was passed to a continuous counter-current extracting tower.

At the continuous counter-current extracting tower, water was added dropwise from the top and the aforesaid oil phase was supplied from the bottom. The amount of supporting electrolyte salt contained in the oil phase Was extracted to less than 0.3% with water in an amount of only one-eighth the amount of the oil phase.

Adiponitrile was recovered by distillation of the treated oil phase.

Similar results were obtained when operation was conducted at a pH of 4.5.

EXAMPLE 3 l The electrolysis cell of Example 26 was used, and as an anolyte, 1-N sulfuric acid solution was circulated at a flow velocity of 30 cm./ sec.

An emulsion consisting of parts of an aqueous phase and 50 parts of an oil phase was supplied to the cathode compartment and circulated at a flow velocity of 30 cm./sec. and electrolyzed at 40 C. with a current of 10 amperes.

The composition of aqueous phase of the emulsion supplied to the cathode compartment was 6.1% of acrylonitrile, 15.4% of adiponitrile, 0.4% of propionitrile, a Very small amount of bis-cyanoethyl ether, 0.11% of acrylonitrile oligomer, 58.5% of water, 15.0% of tetraethylammonium p-toluene sulfonate, and 3.5% of ammonium p-toluene sulfonate, and its pH was 6.

The composition of oil phase was 23.2% of acrylonitrile, 58.5% of adiponitrile, 1.6% of propionitrile, 4.1% of acrylonitrile oligomer, 6% of water, 5% of tetraethylammonium p-toluene sulfate, and 1% of ammonium ptoluene sulfate. The adiponitrile, propionitrile, bis-cyanoethyl ether and acrylonitrile were recirculated electrolysis products.

During the operation of electrolysis, the composition of influent emulsion of cathode was kept at the aforesaid value, and homogenized influent emulsion by the addition of acrylonitrile was electrolyzed for 100 hours. Analysis showed a selectivity of 2.5 for propionitrile, 91.0% for adiponitrile, 6.3% for acrylonitrile oligomer, and 0.2% for bis-cyanoethyl ether. The effluent emulsion of cathode was discharged from the catholyte tank and settled to separate the oil phase. To separate supporting electrolyte salt dissolved in this oil phase, it was treated in a continuous counter-current extracting column.

In this continuous counter-current extracting column, water was supplied dropwise from its top, and oil phase was supplied from the bottom. By extracting the oil phase with water in an amount as small as one-eighth the amount of oil phase, it was possible to lower to less than 0.03% the amount of supporting electrolyte salt contained in the oil phase.

Adiponitrile was recovered by the distillation of the treated oil phase.

EXAMPLE 32 The same electrolysis cell as in Example 26 was used, except the cathode was made of platinum, and a 1.5-N sulfuric acid solution was circulated as the anolyte at a flow velocity of cm./ sec.

An emulsion consisting of 50 parts of aqueous phase and 150 parts of oil phase was supplied to the cathode compartment and circulated at a flow velocity of 70 cm./ sec. and electrolyzed at C. at a current of 7 amperes.

The composition of aqueous phase of the emulsion supplied to the cathode compartment was 2% of acrylonitrile, 2% of adiponitrile, 80% of water, 11% of lithium chloride, and 4% of hexamethylenediamine benzene sulfonate, and its pH was 4.

The composition of oil phase was 46% of acrylonitrile, 36% of adiponitrile, 5% of water, 0.2% of lithium chloride, and 2% of hexamethylene diamine benzene sulfonate. The electrolysis was continued for 20 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity for the electrolysis product was 14% for propionitrile, 78% for adiponitrile, 8% for acrylonitrile oligomer, and 0.1% for bis-cyanoethyl ether.

EXAMPLE 33 When each of the foregoing examples is repeated under the conditions of Examples la and 18a, i.e., utilizing a solution corresponding to the aqueous phase of the catholyte in place of the emulsion, results corresponding to Examples la and 18a are obtained, i.e., propionitrile selectivity substantially increases at the expense of the adiponitrile selectivity, and polymer deposits in the cathode compartment and on the cathode during operation, which finally interferes with continued operation.

In the same manner, when each of the above mentioned examples is repeated following the procedure set forth in Examples 11; and 18b, i.e., with the omission of the anion polymerization inhibitor, polymer deposits on the cathode and in the cathode compartment, eventually clogging the cell.

As may be seen from the foregoing, the electrolytic hydrodimerization of the acrylonitrile in accordance with the invention offers many advantages of the prior known and proposed processes. One prime advantage which can be mentioned is the fact that the novel process will allow, if desired, operation with a lower concentration of aqueous dissolved acrylonitrile than was previously possible and thus allows operation in a range completely outside of the range taught by the prior art. Operation within this new range, which is possible for the first time in accordance with the invention, has many advantages, such as reduction in the formation of the oligomer, the possibility of use of less expensive supporting electrolyte salts, and facility in product separation and recovery. Furthermore, when operating in accordance with the invention, it becomes possible for the first time to obtain an almost quantitative yield of adiponitrile and to operate for prolonged periods without a progressive decrease in adiponitrile selectivity or yield.

The problem of polymer formation during the electrolysis has always been recognized in the art and the prior art attempts to suppress the same, as for example by addition of a free radical type polymerization inhibitor, has always proven unsuccessful. The solution of this problem for the first time in accordance with the invention is based on the discovery that the polymerization problem does not arise from a free radical type polymerization but arises from an entirely different polymerization mechanism, which arises not from the formation of free radicals but is caused by the electric field or potential which, without intending to be bound by any particular theory, may be termed an anion polymerization mechanism. In any event, the addition of the anion polymerization inhibitor, in accordance with the teaching of the invention, effectively prevents the prior-occurring polymerization problem and effectively eliminates the problem of polymer deposit and clogging, which conventionally occurred at the cathode and in the cathode compartment, and furthermore suppresses propionitrile formation which can be attributed to such deposits and clogging.

While in accordance with the invention the additional presence of a free radical type polymerization inhibiator, as for example hydroquinone and the like, is not excluded, it is clear that such free radical polymerization inhibitors .are completely ineffective in suppressing the type of polymerization which is a problem in the cathode chamber.

Again, without intending to be limited by any theory, it is believed that with the use of the emulsion as opposed to a solution as the catholyte, the combination of the continuous aqueous phase and emulsified oil phase at the cathode effectively prevents a gradient type acrylonitrile depletion in the area of the cathode surface and tends to make acrylonitrile accessible and available to the cathode surface for the effective hydrodimerization. The anion polymerization inhibitor is believed to not only effectively prevent a polymerization which would be likely to occur in the concentrated oil phase, but for some reason maintains the cathode surface activated for the hydrodimerization reaction and suppresses propionitrile formation. This action may be aided by the use of protective colloids and, as mentioned, the combination of water and a protective colloid in itself will act as an anion polymerization inhibitor, whereas water alone is ineffective for this purpose.

We have discovered that the anion polymerization inhibitor is not only effective when using the above described emulsion-type catholyte, but also presents substantial advantages when present in an electrolytic dimerization utilizing a solution-type catholyte. Thus, in accordance with a further embodiment of the invention, the electrolytic hydrodimerization of acrylonitrile, utilizing a catholyte in the form of an aqueous solution containing dissolved acrylonitrile and a supporting electrolyte salt, preferably of the type previously described, is improved by adding an anion polymerization inhibitor as above described to such a solution-type catholyte. The electrolysis utilizing the solution-type catholyte may otherwise be effected in any of the known or conventional modes, and the anion polymerization inhibitor may be added in amounts ranging between 10 ppm. and 10% by weight of the entire catholyte.

This further production of the invention is illustrated by the following examples given by way of illustration and not limitation:

EXAMPLE 34 An electrolysis cell which had a lead cathode with a surface area of 10 cm. x 10 cm. and a lead-antimony anode with the same area was use-d. The anode compartment and cathode compartment of the cell were partitioned by cation exchange membrane formed of sulfonated divinyl benzene-styrene-butadiene copolymer of 1 mm. in thickness. The dimensions of the cathode compartment and the anode compartment of the electrolysis cell were 10 cm. in length, 10 cm. in width, with 1 mm. distance between the electrode surface and membrane surface maintained by spacers. The anolyte was circulated by pump between the anode compartment and the anolyte tank, and the catholyte was also circulated by pump be tween cathode and catholyte tank. As anolyte, a 2-N sulfuric acid solution was circulated. at a flow rate of 30 cm./sec.

The catholyte was an aqueous solution of 6.0% of acrylonitrile, 2% of adiponitrile, 0.1% of propionitrile, a trace amount of biscyanoethyl ether, 0.1% of acrylonitrile oligomer, 71.3% of water, 17.0% of tetraethyl ammonium sulfate, 3.5 of hexamethylene diamine p-toluene sulfonate, and its pH was 3. The adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer were recirculated electrolysis product. During electrolysis, acrylonitrile was added to the effiuent solution of cathode compartment for the extraction of the electrolysis products and the resultant aqueous solution of eflluent was adjusted to the aforesaid composition and recycled. The electrolysis was continued for 300 hours. In the terms of acrylonitrile consumed, the percentage of selectivity of each product was 6% for propionitrile, 88% for adiponitrile, 5.8% for acrylonitrile oligomer and 0.2% for bis-cyanoethyl ether.

After the extraction of adiponitrile by addition of acrylonitrile and separation into an oil phase, the oil phase was passed through a continuous counter-current extracting column.

In this continuous counter-current extracting column, water was supplied dropwise from its top and oil phase was supplied from the bottom. By extracting the oil phase with water in an amount as small as one-tenth the amount of oil phase, it was possible to lower to less than 0.03% the amount of a supporting electrolyte salt contained in the oil phase.

Adiponitrile was recovered by the distillation of the treated oil phase.

When the solution containing the anion polymerization inhibitor in the catholyte solution was electrolyzed in this way, adiponitrile was formed at a high selectivity, no polymer was formed, and the selectivity to propionitrile did not increase over a prolonged period of operation.

In place of hexamethylene diamine p-toluene sulfonate, hexamethylene diamine sulfate, N,N'-dimethyl hexamethylene diamine acetate or dicyanoethylhexamethylene diamine maybe used with the same results.

EXAMPLE 34a Example 34 was repeated except that hexamethylene diamine p-toluene sulfonate was not added to the catholyte solution. The infiuent solution of the cathode compartment was thus adjusted to a composition of 6.0% of acrylonitrile, 2% of adiponitrile, 0.1% of propionitrile, a trace amount of biscyanoethylether, 0.1% of acrylonitrile oligomer, 74.5% of water and 17.0% of tetraethyl ammonium sulfate, and its pH was adjusted to 3. This influent solution was supplied to the cathode compartment at a flow velocity of 30 cm./sec. 'Ihe electrolysis was conducted with an electric current of amperes at a temperature of 50 C. By analysis of the cathode solution after 100 hours of operation, the percentage of selectivity in terms of acrylonitrile consumed by electrolysis was 91.8% for propionitrile, 8.0% for adiponitrile, 1.0% for oligomer and 0.2% for biscyanoethyl ether. Some amounts of polymer were deposited in the cathode compartment and on the cathode surface and the selectivity of propionitrile gradually increased and that of the adiponitrile decreased during the electrolysis. Accordingly it was not possible to maintain operation of electrolysis successfully under such conditions for a long period.

EXAMPLE 35 The electrolysis cell of Example 34 was used, except that the cathode was made of lead alloy containing 7% of antimony. l-N sulfuric acid solution as anolyte was used, circulating at a flow velocity of 30 cm./sec. In the cathode compartment, an aqueous solution was supplied and circulated and electrolyzed at 50 C. at a current of 10 amperes.

The composition of aqueous solution in the cathode compartment was of acrylonitrile, 19.2% of adiponitrile, 1.5% of propionitrile, a trace amount of biscyanoethyl ether, 0.5% of acrylonitrile oligomer, 38.8% of water, 23.0% tetraethyl ammonium p-toluene sulfonate, p.p.m. of methyl cellulose, and 3.0% of triethylamine sulfate, and its pH was 8. The adiponitrile, propionitrile, biscyanoethyl ether and acrylonitrile oligomer were recirculated electrolysis products. During the electrolysis, acrylonitrile was added to the effluent solution of the cathode compartment, and the resultant aqueous solution was adjusted to the aforesaid composition. The electrolysis was conducted for 300 hours. In terms of acrylonitrile consumed by electrolysis, the percentage of selectivity was 7.1% for propionitrile, 90.0% for adiponitrile, 2.5% for acrylonitrile oligomer, and 0.4% for biscyanoethyl ether.

The effluent emulsion of cathode compartment was discharged from the catholyte tank, acrylonitrile added, and further settled to separate as an oil phase. Adiponitrile was recovered from this oil phase. To separate supporting electrolyte salt dissolved from the oil phase, said oil phase was passed to a continuous counter-current extracting tower.

At the continuous counter-current extracting tower, water was added dropwise from the top, and the aforesaid oil phase was supplied from the bottom. The amount of supporting electrolyte salt contained in the oil phase was extracted to less than 0.03% with an amount of water of only one-eighth the amount of the oil phase.

Adiponitrile was recovered by distillation of the treated oil phase.

EXAMPLE 3511 Example 35 was repeated, except that trimethylamine sulfate and methyl cellulose were not added to the solution supplied to the cathode compartment. The influent solution of cathode compartment was thus adjusted to a composition of 15% of acrylonitrile, 19.2% of adiponitrile, 1.5% of propionitrile, a trace amount of biscyanoethyl ether, 0.5 of acrylonitrile oligomer, 42% of water and 23.0% of tetraethyl ammonium sulfate, and had a pH of 8.1. This infiuent solution was supplied to the cathode compartment at a flow velocity of 30 cm./sec. The electrolysis was conducted at a current of 10 amperes at 50 C. As the anolyte solution, a 1-N sulfuric acid solution was used and circulated at 30 cm./sec. Of acrylonitrile consumed by electrolysis during 200 hours of operation, 85.0% was converted to propionitrile, 12.4% to adiponitrile, 1.8% to oligomer, and 0.8% to biscyanoethyl ether.

At this time, when the electrolysis cell was disassembled, acrylonitrile polymer was found accumulated in the cathode compartment. At the end of electrolysis, it was found that the selectivity for propionitrile increased gradually, while the selectivity for adiponitrile decreased. Under such conditions, therefore, it was not possible to continue electrolysis successfully for a long period.

EXAMPLE 3 6 The electrolysis cell had a cathode made of pure lead with a surface area of 10 cm. x 10 cm. and an anode made of lead-antimony alloy with the same surface area. The dimension of the cathode compartment and the anode compartment was 10 cm. in length and 10 cm. in width and had 2 mm. distance between the electrodes and membrane surface. An aqueous solution was supplied and circulated to the electrolysis cell at the flow rate of 20 cm./sec., and electrolyzed at 20 C. with a current of 10 amperes.

The composition of the aqueous solution in the cathode compartment was 8.5% of acrylonitrile, 8.5% of adiponitrile, 62.8% of water, 17.0% of tetraethyl ammonium ethosulfate, 100 p.p.m. of methyl cellulose, and 3.5% of N,N'-dimethylhexamethylene diamine p-toluene sulfonate, and its pH was 6. In terms of acrylonitrile consumed during electrolysis, the percentage of selectivity was 12.0% for pro-pionitrile, 85.0% for adiponitrile, 2.5 for acrylonitrile oligomer, and 0.5% for biscyanoethyl ether. On

the contrary, when a solution without the N,N-dimethylhexamethylene diamine p-toluene sulfonate as the anion polymerization inhibitor was electrolyzed, acrylonitrile polymer was accumulated during electrolysis and the formation of propionitrile was increased gradually, and consequently, it was impossible to electrolyze for a long period.

EXAMPLE 37 The electrolysis cell of Example 34 was used. As the anolyte, l-N sulfuric acid solution was circulated at the flow velocity of cm./sec. An aqueous solution was supplied to the cathode compartment and circulated at the flow velocity of cm./sec., and electrolysis was operated at a current of 10 amperes and 50 C.

The composition of the aqueous solution used as the catholyte was 16% of acrylonitrile, 18% of adiponitrile, 36.5% of water, 23.0% of benzyltriethylammonium sul fate, and 3.5% of ammonium naphthalenesulfonate, and its pH was 7.1.

In terms of acrylonitrile consumed during the electrolysis, the percentage of selectivity was 7.3% for propionitrile, 86% for adiponitrile, 6.1% for acrylonitrile oligomer, and 0.6% for biscyanoethyl ether.

When using 2% of dimethylamine laurylsulfonate and 0.2% of naphthylamine, respectively, instead of the ammonium naphthalenesulfonate as the anion polymerization inhibitor, the same results as in this example were ob tained.

EXAMPLE 38 A similar electrolysis cell and the same anolyte as used in Example 34 was used. The catholyte was of a heterogeneous phase and was circulated in the suspended state at a flow rate of 10 cm./ sec. The catholyte was composed of 160 g. of acrylonitrile, 160 g. of adiponitrile, 72 g. of water, 8 g. of tetraethylammonium p-toluene sulfonate, and 2 g. of ammonium naphthalene sulfonate, and its pH was 3. The electrolysis was performed with 1 dm? of cathode area, at a current density of 10 amperes/dmP, and C. After two hours of operation, the electrolysis cell was dismantled and examined, which had substantially no formation of polymer of acrylonitrile on the cathode surface.

EXAMPLE 39 A similar electrolysis cell and the same anolyte as used in Example 34 was used. This catholyte was of a heterogeneous phase and was circulated in the suspended state at a flow velocity of 30 cm./ sec. The composition of catholyte was 320 g. of acrylonitrile, 64 g. of Water, 16 g. of tetraethylammonium sulfate, 3 g. of diethylamine lauryl sulfate, and 0.4 g. of u-naphthylamine, and its pH was 4. The area of cathode was 1 dm. The electrolysis was operated at the current density of 10 amperes, and at the temperature of 35 C. After two hours of operation, the electrolysis cell was disassembled and examined, which had substantially no formation of polymer on the cathode surface.

While the invention has been described in detail with reference to certain specific embodiments, various changes and modifications which fall 'within the spirit of the invention and scope of the appended claims will become apparent to the skilled artisan. The invention is thus only intended to be limited by the appended claims, or their equivalents, wherein we have endeavored to claim all inherent novelty.

We claim:

1. A method of producing adiponitrile by the electrolytic hydrodimerization of acrylonitrile, which comprises passing an electrolyzing electric current through an emulsion having an oil phase and a continuous aqueous phase, said emulsion containing a supporting electrolyte salt, acrylonitrile and an anion polymerization inhibitor, said acrylonitrile being distributed in the aqueous phase as dissolved acrylonitrile and in the oil phase in suificient quantity to supply additional acrylonitrile to the aqueous phase upon acrylonitrile depletion in that phase, said anion polymerization inhibitor being present in amount sufiicient to substantially suppress electric current-induced polymerization of acrylonitrile in the emulsion.

2. Method according to claim 1 in which said supporting electrolyte salt is a quaternary ammonium salt.

3. Method according to claim .2 in which said quaternary ammonium salt is a quaternary ammonium salt of low oleophilic property.

4. Method according to claim 3 in which said salt does not contain more than a total of 10 carbon atoms connected to the nitrogen.

5. Method according to claim 1 in which the aqueous phase of said emulsion has a pH between 1 and 10.

6. Method according to claim 1 in which said emulsion is maintained in contact with a cathode formed of a metal selected from the group consisting of copper, cadmium, tin, lead, mercury and alloys thereof.

7. Method according to claim 1 in which said supporting electrolyte salt is a salt selected from the group consisting of alkali and alkaline earth metal salts, ammonium salts and quaternary ammonium salts.

8. Method according to claim 1 in which said supporting electrolyte salt is selected from the group consisting of aliphatic quaternary ammonium, aromatic quaternary ammonium, and heterocyclic quaternary ammonium sulfates, halides, phosphates, aryl sulfonates, aralkyl sulfonates, alkyl sulfates and carboxylates.

9. Method according to claim 1 in which said emulsion contains an organic diluent.

10. Method according to claim 1 in which said emulsion contains a protective colloid.

11. Method according to claim 1 in which said anion polymerization inhibitor is selected from the group consisting of amines, ammonia, amine salts, ammonia salts, alcohols, organic acids, inorganic acids, acetylene compounds, oxygen, carbon monoxide, carbon dioxide, carbon oxysulfide, mercaptans, carbon sulfide, carbon disulfide and dialkyl sulfide.

12. Method according to claim 1 in which said anion polymerization inhibitor is selected from the group consisting of hexamethylene diamines and hexamethylene diamine salts.

13. Method according to claim 1 in which said anion polymerization inhibitor is a member selected from the group consisting of dimethyl hexamethylene diamine, cyanoethylated hexamethylene diamine, hexamethylene diamine and salts thereof.

14. Method according to claim 1 in which said anion polymerization inhibitor is one containing an active hydrogen atom.

15. Method according to claim 1 in which the electrolytic hydrodimerization is effected in an electrolytic cell having cathode and anode compartments separated by a diaphragm and in which the catholyte emulsion is circulated through the cathode compartment in contact with the cathode, and in which the anolyte is in the form of a mineral acid.

16. Method according to claim 15 in which said diaphragm is a cation exchange membrane.

17. Method according to claim 1 in which said anion polymerization inhibitor is a compound capable of reducing the negativity of the doubte bond of acrylonitrile.

18. Method according to claim 1 in which said supporting electrolyte salt is present in the aqueous phase of said emulsion in amount of about 1 to 60% and said anion polymerization inhibitor is present in amount of about 10 ppm. to 20% by weight.

19. A method of producing adiponitrile by the electrolytic hydrodimerization of acrylonitrile which comprises passing an electrolyzing electric current through an emulsion having an oil phase and a continuous aqueous phase, said emulsion containing a supporting electrolyte salt, acrylonitrile and an anion polymerization inhibitor,

said acrylonitrile being distributed in the aqueous phase as dissolved acrylonitrile in a concentration of less than about by weight and in the oil phase in sufficient quantity to supply additional acrylonitrile to the aqueous phase upon acrylonitrile depletion in that phase, said anion polymerization inhibitor being present in amount sufiicient to substantially suppress electric current-induced polymerization of acrylonitrile in the emulsion.

20. Method according to claim 19 in which said supporting electrolyte salt is a quaternary ammonium salt.

21. Method according to claim 20 in which said quaternary ammonium salt is a quaternary ammonium salt of low oleophilic property.

22. Method according to claim 21 in which said salt does not contain more than a total of carbon atoms connected to the nitrogen.

23. Method according to claim 19 in which the aqueous phase of said emulsion has a pH between 1 and 10.

24. Method according to claim 19 in which said emul sion is maintained in contact with a cathode formed of a metal selected from the group consisting of copper, cadmium, tin, lead, mercury and alloys thereof.

25. Method according to claim 19 in which said supporting electrolyte salt is a salt selected from the group consisting of alkali and alkaline earth metal salts, ammonium salts and quaternary ammonium salts.

26. Method according to claim 19 in which said supporting electrolyte salt is selected from the group consisting of aliphatic quaternary ammonium, aromatic quaternary ammonium, and heterocyclic quaternary ammonium sulfates, halides, phosphates, aryl sulfonates, aralkyl sulfonates, alkyl sulfates and carboxylates.

27. Method according to claim 19 in which said emulsion contains an organic diluent.

28. Method according to claim 19 in which said emulsion contains a protective colloid.

29. Method according to claim 19 in which said anion polymerization inhibitor is selected from the group consisting of amines, ammonia, amine salts, ammonia salts, alcohols, organic acids, inorganic acids, acetylene compounds, oxygen, carbon monoxide, carbon dioxide, carbon oxysulfide, mercaptans, carbon sulfide, carbon disulfide and dialkyl sulfide.

30. Method according to claim 19 in which said anion polymerization inhibitor is selected from the group consisting of hexamethylene diamines and hexamethylene diamine salts.

31. Method according to claim 19 in which said anion polymerization inhibitor is a member selected from the group consisting of dimethyl hexamethylene diamine, cyanoethylated hexamethylene diamine, hexamethylene diamine and salts thereof.

32. Method according to claim 19 in which said anion polymerization inhibitor is one containing an actve hydrogen atom.

33. Method according to claim 19 in which the electrolytic hydrodimerization is effected in an electrolytic cell having cathode and anode compartments separated by a diaphragm and in which the catholyte emulsion is circulated through the cathode compartment in contact with the cathode, and in which the anolyte is in the form of a mineral acid.

34. Method according to claim 33 in which said diaphragm is a cation exchange membrane.

35. Method according to claim 19 in which said anion polymerization inhibitor is a compound capable of reducing the negativity of the double bond of acrylonitrile.

36. Method according to claim 19 in which said supporting electrolyte salt is present in the aqueous phase of said emulsion in amount of about 1 to 60% and said anion polymerization inhibitor is present in amount of about 10 p.p.m. to by weight.

37. Method according to claim 19 in which said emulsion contains a dissolved organic diluent selected from the group consisting of adiponitrile and propionitrile in 36 amount suificent to maintain a concentration of the acrylonitrile dissolved in the aqueous phase below said 5% value.

38. A method of producing adiponitrile by the electrolytic hydrodimerization of acrylonitrile in an electrolytic cell having a cathode compartment separated by a diaphragm from an anode compartment, which comprises circulating a catholyte in the form of an emulsion having an oil phase and a continuous aqueous phase through the cathode compartment in contact with the cathode, and circulating an anolyte in the form of a mineral acid through the anode compartment while passing an electric current at a density between about 3 and 30 amps per square decimeter :between the anode and cathode, said catholyte emulsion having a pH between 1 and 10 and a weight ratio of the oil phase to the aqueous phase between 511 and 1:100 and containing a quaternary ammonium sulfate electrolyte salt in amount of about l% by weight, an anion polymerization inhibitor selected from the group consisting of dimethyl hexamethylene diamine, cyanoethylated hexamethylene diamine, hexamethylene diamine and salts thereof, in amount of 10 p.p.m. to 10% 'by weight, and acrylonitrile, said acrylonitrile being distributed in the aqueous phase as dissolved acrylonitrile in amount of between about 2 and 5% and in the oil phase in amount of between about 1 and 99%.

39. Method according to claim 38 in which said emulsion additionally contains a protective colloid and an organic diluent comprising at least one electrolysis product.

40. Method according to claim 39 in which said anolyte is an aqueous sulfuric acid solution and said diaphragm a cation exchange membrane.

41. Method of producing adiponitrile by the electrolytic hydrodimerization of acrylonitrile which comprises passing an electrolyzing electric current through an emulsion having an oil phase and a continuous aqueous phase and containing a quaternary ammonium electrolyte salt and acrylonitrile, said acrylonitrile being distributed in the aqueous phase as dissolved acrylonitrile and in the oil phase in sufficient quantity to supply additional acrylonitrile to the aqueous phase upon acrylonitrile depletion in that phase.

42. Method according to claim 41 in which the aqueous phase of said emulsion has a pH between about 1 and 10.

43. Method according to claim 41 in which said supporting electrolyte salt is selected from the group consisting of aliphatic quaternary ammonium, aromatic quaternary ammonium and heterocyclic quaternary ammonium sulfates, halides, phosphates, aryl sulfonates, aralkyl sulfonates, alkyl sulfates and carboxylates.

44-. Method according to claim 41 in which said emulsion contains a protective colloid.

45. Method according to claim 41 in which said supporting electrolyte salt is a quaternary ammonium sulfate.

46. Method according to claim 41 in which the electrolytic hydrodimerization is effected in an electrolytic cell having cathode and anode compartments separated by a diaphragm and in which the catholyte emulsion is circulated through the cathode compartment in contact with the cathode, and in which the anolyte is in the form of a mineral acid, said emulsion containing a ratio of the oil phase to the aqueous phase varying between 5:1 and 1:100.

47. Method according to claim 46 in which said diaphragm is a cation exchange membrane.

48. A method of producing adiponitrile by the electrolytic hydrodimerization of acrylonitrile which comprises passing an electrolyzing electric current through a catholyte having a pH between 1 and 10 in th form of an emulsion having an oil phase and a continuous aqueous phase, and containing a supporting electrolyte salt and acrylonitrile, said acrylonitrile being distributed in the aqueous phase as dissolved acrylonitrile and in the oil phase in sufficient quantity to supply additional acrylonitrile to the aqueous phase upon acrylonitrile depletion in that phase, said emulsion having a weight ratio of the oil phase to the aqueous phase between about 5:1 and 1:100.

49. Method according to claim 48 in which said catholyte contains a protective colloid.

50. In the method of producing adiponitrile by the electrolytic hydrodimerization of acrylonitrile in which an electric current is passed through a catholyte in the form of an aqueous solution containing acrylonitrile and a supporting electrolyte salt, the improvement which comprises utilizing the catholyte additionally containing a protective colloid sufficient to substantially suppress electric current induced acrylonitrile polymerization.

51. Improvement according to claim 50 in which said protective colloid is a member selected from the group References Cited UNITED STATES PATENTS 2,726,204 12/1955 Park et al. 20472 FOREIGN PATENTS 277,308 6/1964 Australia 204-74 JOHN H. MACK, Primary Examiner R. L. ANDREWS, Assistant Examiner 

